Brother it's probably the way your fishing it. Look up the Big Horn Method! From what I hear you saying and seeing as I haven't yet to wet a line in that river it's appears as if it's the method in which your attempting to fish that fly! I'd love to draw out the entire rig for you from running line to your last fly. It looks pretty crazy but seems to work for those fish feeding in the vegitation.
The big horn river is chalked full of grass, so much so that you don't even see a vast majority of those 18''+ fish that fill that river. The big horn river is one of the most densly populated rivers in the conjoined states and if your not fishing it right you will have a rough day. We had two of those days and then figured out this method! The best advise I know to give is don't give up and take your indicator all the way up until it almost reaches your running line on a 9' leader. Big upstream mends, drift, drift, set, set, set!