-atk +res Brave Ike

depends.
If you're someone who doesn't/can't put money into this game, then sure, build units you like. Is it optimal for arena? no.

It all comes down to how you play the game and if you're gonna have to spend limited resources on building him.

I'd say just build his default kit up (its actually pretty nice) and try it out. If he under performs, look for other units to fill the spot.

Second piece of advice would be go ahead and farm all of the new free orbs and try to get brave ike again (only if you really want ike and dont have other units you're also trying to get)

A little scattered but hope this helps bud

Yes, he's worth it.

I have the same IV Ike and, believe it or not, he's a good magic tank.
With a +3 hp seal, he sits at 46 hp and 23 resistance.

Basically, he can survive any mage that hits him for 38 x2 damage or less, which means any mage needs 62 attack (including color modifiers) to kill Ike I'm one round. That's pretty hard to get, especially since flyers and carry lose any bonuses they've received.

Best part is, if he survives, he's just taken 2 hits to his face. Couple with steady breath, each hit he takes removed 2 from his charge for aether, which is already at a -1 cooldown from his axe.
So he will survive most mages and activate aether for the follow up the following turn.