I was excited about making a magus. However I realized that casting defensively means a magus won't be able to be sure they can get off shocking grasp 100% of the time until around level 10 or so.
For example, a level 2 elven magus with 16 int and the right trait would have a concentration of 7 and need to make a 17 to not lose the spell. So that is a 55% chance of success. That's not a nova once you consider you can do that 2 to 3 times a day with 1 handed weapon....with 1 or maybe 2 getting cast and maybe 1 landing. That's not even barbarian damage. Sure, you could arcane mark for another attack with only a 15 dc, with a 65% chance of success....but that still isn't very good odds. Plus it requires a full attack to work.
I am kind of at a loss on why a magus is decent before level 8 or so. Can you explain it, because they seem worse than rogues before then.
Various feats and traits can add to concentration.
Also under the magus spell combat section:
"If he casts this spell defensively, he can decide to take an additional penalty on his attack rolls, up to his Intelligence bonus, and add the same amount as a circumstance bonus on his concentration check."
Giving you a potential +3 more (granted you will probably miss your attack rolls that round), but that is better than simply losing the spell. Which means every other turn expect to kick out a lot of damage at worst, and at best when you get in a lucky hit despite the attack penalty you still kick out a lot of damage in a single round.
Remember also with touch attack spells you can hold the charge if you miss. So failing to hit doesn't mean your spell is lost, it just means you apply it the following round. Or with spellstrike you apply it through your weapon then get to cast another spell as well and try a touch attack. This means in some rounds you could get two spells worth of damage off.
At 3rd level you can take arcana to counterbalance your lost to hit chance (Arcane Accuracy) or to once per day reroll a failed concentration check (Concentrate) or to add to your AC so you aren't as likely to be hit and don't have to cast defensively (Spell Shield). At higher levels even more options open up.
Also because magus gain access to new spell levels every 3rd level instead of every 2nd level you quickly out pace (because of level) the penalty for defensive casting.
At 4th level pick up mirror image (or blur, or both) and cast that before entering the fray. With a full mirror image set chances are you won't need to cast defensively.
Cast 10 feet away, 5 foot step attack. You get the touch attack as part of the casting and you can take a 5 foot step during a full round action (spell combat).
So cast while out of range avoiding having to make a concentration check.Step in and attack.
This would only work if you started 10 feet away for some reason, which is weird, and the monster doesn't have reach.
@james- what is the elven alternative trait that adds to concentration checks.