It does take some getting used to. In the past I've made the mistake of using a 4wt and then adding alot of shot/putty to get the fly down in heavy current. A light fly line won't cast that rig as well as a 5/6 wt. which works better for me.
I assume you're nymphing or using a bugger, you don't necessarily want to "back cast" those rigs all the time. A short lob cast won't tangle as easily. This is also true with mulit-fly rigs.
Also, how far up are you placing the weight? Your post says you're weight is on the leader, I place mine 8 inches or so up from the fly which is all tippet, not on the leader itself.
I'm not sure if this makes sense, but this is how I look at it, especially for weighted tandem fly rigs. Try and treat the weighted rig as a delicate assembly. It's not like tossing a dry fly where you can back cast and really work the line. Try and keep that weight and fly rig in a straight line, the more you practice this the more natural it will become. Then in wind or if you miss a strike you'll still get tangles but that's another story.
I think I've read that you fish Bowmans Creek, I'm out there quite a bit. If you ever want to meet up I'll be glad to join you.
I'm still a newbie myself but have been lucky to have some guidance from experienced fly guys.