If you're working up loads for heavy guns, yes it helps. If you're learning to shoot those heavy guns, then no. Unless you pack one while hunting.
I use my lead slid to work out loads for my heavy rifles (375H&H, 416 Rigby, 458 WM, etc) but once I get the load I quite and go back to shooting pretty how I'm going to shoot in the field, with those rifles its not too bad because I think they are pretty much off hand or knelling rifles ( positions you'll encounter while hunting.
For good off hand practice I use cast bullets and reduced loads.
I'm not really sure if I didn't have a lead slid, I'd get one. I don't use it that much and its always in the way.
CPT USAR Ret
USAMU Sniper School Oct '78
Distinguished Rifle Badge 1071