ah 17, that's right, the huge 4 parter. all i did through all the parts was put my units that can survive just on the range of enemies, so they attack, then my weaker defense units or just some other units go and attack them and finish them(if they aren't already dead) then charge to the next line and pull back whoever is in range that i don't want to get hit. though i'd have to say the 3rd part where you find reyson's sister is the most annoying cause you're surrounded, so just about everyone is in range. what i do is head out my strong units to finish off the more effective units like mages and archers that will own my flying units. that one is probably the hardest part. i didn't have a healer so i think you should bring one :P but guard him well. since my ike was already level 20(ever since chapter 14 i think) i didn't use him at all except to finish units if i was in trouble, and since he has leanna(i think that's her name) on his back for a chapter, he becomes almost useless. bring long range units, fast units, and good defense units and it should be fine. it wasn't too hard.