non-casters don't have enough viable options built-in. with so few non-combat abilities gained through class features, non-casters are forced to rely on feats, items and skills to get viability out of combat.
-most of a non-caster's feats will be used to make it a better combatant. with 10 feats on average (6 from levels, 1 from level 1, and a few from class/crossclassing), very few characters take their first few feats to get extra non-combat options, especially if they're going for a particular style of combat. this leaves us with skills an items
-there are 36 skills listed in core book. only 3 out of 11 classes get 6+int or more skill points per level. only one of the 8 classes that get 4 or less actually use Int to really power class abilities (wizard). this means the average int (10-11) character knows about 10th of the skill list, and of what little he can learn a large part is cross-classed, which makes it far harder to be properly trained in it
-so items. a non-caster eventually becomes VERY reliant on their items to be successful. the main problem is that items may or may not be accessible. while the game assumes they generally are, these items REQUIRE a caster to create them. effectively telling a non-caster: "to gain options you must emulate the caster, which has options". which kinda sucks.
-the last problem is since the non-casters have so little built-in support for anything that isn't "i hit it with my [weapon of choice]" or "i hit it REALLY hard", non-casters rely almost entirely on the GM's adjudication of player skill and metagame information when it comes to options. that might be ok for some people, but it really grinds my gears that Edward the Headsman's ability to bypass a traps is reliant on Oxybe the Player's ability to creatively use a crowbar, a pully, several dozen yards of rope, a handful of pitons and a log.
------------------------------------------------------
problems with casters:
-too many options. most of the early casters were built to be catch-all archetypes. the wizard is meant to be Gandalf, Elminister, Tim the Enchanter, Dumbledore, etc... while many of the non-casters were built around very specific archetypes, like the savage Barbarian or the wuxia-influenced Monk.
the problem with this is the your wizard, cleric, druid or whatnot could change each day if he wanted to if he was Gandalf, Elminister, Tim the Enchanter, Dumbledore, John the Horrible Necromancer from down the lane, etc... or worse, in one day simply amalgam the stronger aspects of these and wreck havoc as flying, invisible, huge-sized, man-eating millipede that has a furnace for a stomach.
-too many "i win" or Win/Lose binary spells. a lot of spells simply did stuff... and a lot of this stuff was quicker or more reliable then what the non-casters could do.
want to go over the chasm? polymorph into a bird/fly/teleport/etc...
want information from the NPC? change his attitude via magic/force him to give you information via dominate or kill+speak with dead.
want to know what is in store for you/what could help? divination. divination. divination.
a lot of these types of spells could be gained quickly enough and scribing a scroll or two of situational spells is a drop in the bucket money-wise. a bit later on, you can easily craft wands / staves for these spells and with splats runestaves that let you convert prepared spells into those on the staff.
-many spells were simply better then the non-spellcaster options. a slightly less then 500 GP collection per PC (assuming a 5 person group) would allow a 5th level wizard to create a wand of Open Lock that has a 100% success rate per lock (50 in total) and can be used at a safe distance to open the locks on most doors without fear of getting hit by the trap. note that is effectively paying 10GP per lock picked, per group member, magical lock or otherwise.
an unseen servant can be used to open the doors. and a wand thereof is quite cheap to make 75GP a PC if you don't feel like risking a PC opening it.
and this is if you're worried about the locks+doors. there are several dungeon bypass spells at later levels that simply allow you to obliterate the door from a safe distance, or just go through the wall adjacent to the door.
a flight spells is in almost all situations better then the jumping or climbing option, and alter self (beast shape/elemental body/whatever) into a creature with a swim speed is far safer then swimming.
i think you can see my point.
and this is simply based on non-combat options alone. in combat a decent spellcaster can usually debuff or cause enough issues to the enemy side in one or two turns that the non-casters are effectively the mop-up crew.
