Their talents make difference.
if this game was just about power, it would be very very boring. You need to get power that actually makes your lineup powerful. For instance, lots of defensive power (runes/gear) on the last target your enemy will attack is basically worthless power. And damage power (runes/gear) on the first target is also basically worthless.
Right idea with these comments but not totally true. Alot of attack power in the front works for some occasions. Alot of defensive power in the back works for some occasions. This is the fun part of the game to me. Figuring out how to defeat different things with what I have to work with. If I add magic defense to this hero will it last one or 2 more rounds to finish killing off that enemy which will then allow me to do this. Etc Etc. There is no set rule that always works for everything in this game.
But having the wrong power on the wrong heroes can cause you lots of problems
I made no mention of front vs back. I said first and last attacked. That was on purpose. You do have to know what types of attacks are coming your way and how to best defend against them. And defensive stats are sometimes useful on damage dealers, since magic and skill shots can hit anywhere.