No, you absolutely do not have to align your fletch with the blades of your broadhead. Using fixed blade heads with your Blazers I'd suggest an offset to optimize spin and stabilization.

On my drop rest, a Trophy Taker pronghorn I actually shoot with cock vane out...when up I have vane contact on my cables and Blazers ares stiff, in time I believe it will cut my cable.

One thing about drop away rests, you don't need to worry about how you shoot your vanes as long as clearances are not an issue.