A blaster is certainly viable. Optimal? Not always, but that's not the question here.
I tend to prefer Sorcerers over Wizards for blasting, since you'll be using a lot of staple spells, and you'll need to be able to put out your best spells more often to keep up in the damage department.
Arcane bloodline is a good one. The bonuses with metamagic and eventually save DC's are nice, and the bloodline spells are consistently useful. A human sorcerer who uses the alternate racial favored class ability will still have a decent selection of spells to deal with various situations.
Since AoE isn't always the best idea, it's good to have some solid single target options in your arsenal. Having the option of targeting different saves is always a great idea, and metamagic rods will be your best friend.
You can be a glass cannon. You have to understand, though, that the glass better be magically treated to more robust than it looks. And, of course, being glass, it's not easy to spot.
What I'm saying is this: The idea of a character who is really frail and helpless when it comes to defence but can devastate enemy armies wholesale is not really a good one. The reason for this is simple: You can have characters who aren't that frail and helpless but still bring the pain.
If you go into blast magic for the damage, it's usually best to do it with area spells. Against a single enemy, you cannot outpace a warrior when it comes to damage output. Quite the opposite: warriors are kings when it comes to obliterating enemies by HP damage one at a time. The fun part for blast mages is that they can usually do the same damage against one or ten enemies.
It can definitely work (despite what some people claim) but it does depend on the party's game style and the circumstances (but that's always the case), and those casters who go straight for the throat (with magic that circumvents HP and straight-up screws the enemy when he fails his save) are often more effective.
If you want to go for the flashy stuff, go right ahead. Just have some other spells, especially protective and utility spells around, too. Spellcasters don't need to overspecialise, which means they really shouldn't.
In terms of spells you can certainly have your Sorcerer glass cannon.
1st - Magic Missile, Ray of Enfeeblement
2nd - Scorching Ray, Acid Arrow
3rd - Fireball (yes, *bows*, thank you very much), Stinking Cloud
4th - Ice Storm, Phantasmal Killer
5th - Cloudkill, Cone of Cold (another stereotype staple)
6th - Acid Fog, Chain Lightning
7th - Delayed Blast Fireball, Finger of Death
8th - Incendiary Cloud, Polar Ray
9th - Power Word: Kill, Meteor Swarm, Weird, Wail of the Banshee
There you go. All killing spells for the "cannon" part of the definition. Flavor the "glass" portion to taste - 8 STR, 8 CON, etc.
You can also have fun with Reach Spell. An Intensified Reach shocking grasp can provide a decent single target damage spell.
I miss the old 3.x Warmage. I hope they bring back some incarnation of it at some point.
I had a character survive her first 10 levels on 35 hp or less before being retired.
It can be done.
Nothing (other than the gods) is immune to everything. Have a variety of energy types and shapes (spreads, cones, rays, lines, etc.) so you can be sure to hurt somebody important. There are some feats and such in the newer books that make the blaster better than it was, and changing energy types can make a wasted spell into a damaging one.
A well-placed area effect can do wonders to clear out mooks in the way of your fighters and the BBEG. Heck, slap him with a few damage spells, too. He'll go down that much quicker. Take spell penetration and some feats to extend the size and effect of area spells, and you can soften up hordes of enemies.
Don't ignore your own need for protection and utility spells for your party, but blasting is far from useless. At least, not as useless as some of the "god-wizard" folks would have you believe.
DPR against a room full of mooks can be impressive. The trick, as always, is to have the right spell for the situation.
Consider looking into the Words of Power system. It lacks a lot of the utility of the standard spellcasting, but what it lacks in utility it makes up for in flexibility, particularly for spontaneous casters. Fighting an enemy that's immune to your Fire Ray? Change one of the words, and now it's a Frost Ray.
Would alternating between damage-over-time spells and direct damage be best? Say, cast that heat metal spell and then hit them with rays while they continue to take the heat damage.
Here we run up against the problem of "1 hit point left, and still swinging like I'm at full." DOT will kill something, eventually. Acid arrow cast over and over will keep peeling off those hit points, but waiting for that lets the bad guy keep acting.
DOT spells are GREAT against enemy casters, though. Anybody casting spells has to make a concentration check when taking ongoing damage, so you could both hurt them and ruin a spell they cast to hurt you.
Would alternating between damage-over-time spells and direct damage be best? Say, cast that heat metal spell and then hit them with rays while they continue to take the heat damage.
Personally I'm a fan of "stacking" spells, especially on tougher targets. Stacking implies that you open with a DOT (Damage over time) spell, and then either another DOT or a spell that lasts for several rounds and is controlled as a move action. A good example of this is the Flaming Sphere. So you Acid Arrow / Heat Metal, then Flaming sphere, then either AoE (Area attack spells) like FireBall or single target such as Scorching Ray.
On really nasty foes dont forget the golden rule: No one is perfect at everything, and that especially applies to saving throws. I brought down the party barbarian at one point with with a classic will save that convinced him the members of his party were actually his enemies who had tricked him into fighting against his friends! LOL What good times.... One especially dirty trick is to learn energy admixture: sound. Why?? Because VERY few things as written in the book are immune to sound. Force is another good choice, for much the same reason.
Another real useful tactic with your spells are summon monster. Keep in mind that a well positioned summoned monster (even if it only has 1 HP) now makes all of your party rogue's attacks sneak attacks, and will give anyone a flanking bonus. Plus if your monsters you have summoned have special attacks, like grapple, there is nothing from stopping you from dropping a pile of them on top of that annoying enemy that keeps running around! Want more fun with summon monster? "Hey Monster, go open that trapped door." BOOM! "Ok guys, all clear."
Last but not least: buff your party with spells like bulls strength, or Mage Armor (works best on a monk due to their lack of armor). Why? Simple, they will LOVE you for it and such actions will encourage them to consider tactics which actually work as a team (god forbid!), and should you start getting hit they now see the danger of loosing their buff buddy who makes them unstoppable. Trust me when i say the value of such things at the gaming table can never be over stated and your party will love having you game with them.
Yes, a glass cannon caster is viable. Good options include:
Sorcerer- Arcane (Sage), Boreal (Rime-blooded), Djinni, Draconic (Linnorm), Efreeti, Elemental (Primal), Marid, Shaitan, Starsoul, and Stormborn are all good bloodlines.
Witch- Elements is probably the best choice of patron, although Vengeance or Winter could also work.
Wizard- Evocation (Admixture) is probably the best choice of school, although Conjuration, Divination (Foresight), or one of the Elemental schools could also work. Since Evocation and Conjuration spells will be your bread and butter, avoid taking them as your opposistion schools.
You may find it worthwhile to be a blaster/controller instead of just a blaster. Keeping your opponents pinned down (controller) gives a better chance of damaging them (blaster). Spells that do both, like black tentacles and wall of fire, should be high on your priority list.