Unfortunately fire type avability in this game is REALLY sparse, which makes Infernape REALLY valuable. Sticking some fire moves on your pokes should be good enough, IMO. Fire isn't that greatly needed in the Elite Four.

After you beat the boss, you should go up to the legendary behind him and fight him (capture if you want). A good place to train following that is the grass by Sunyshore city, which you can get to from Valor Lakefront. It was previously blocked, but the man lets you through after these events. To be honest Staraptor is a LOT better than Noctowl and is pretty helpful in the E4. If you don't mind training him up, he'll be a good help. Dialga/Palkia would also help for the Elite Four if you train them up. A good level for the E4 is with a good team of 6 at 55.