You may be using more hops than you need. For the bulk of your boil, your bittering hops(high alpha) is really all you need. As you boil, you are boiling off any aroma. Then at flame out and dry hop, you should use only your lower alpha aroma hops.
This is not to say that there aren't some terrific high alpha hops that work well as aroma hops or lower alpha hops that work well as bittering hops, however. You might consider doing something like using only one type of hop. Start with something fairly traditional, such as Goldings or Fuggles.