In my experience, if there is any kind of skill difference between the teams, then Reg is awesome for the better team. If it's an even skilled game, Reg is going to be quite useless.
Snipe stops being relevant around level 6. His DPS is fairly low for sieging towers; Mines and Snipe work better. He can't hold a lane at all.
For combat: Any DG > Reg. He goes down very fast.
For support: Any general > Reg. Priest Minions+support skills make Snipe irrelevant from level 1, Angelic Fury doesn't help all that much against Minions, and Mines come too late against Minions.
For siege: Any DG except Assassin Erebus or Ooze UB. Reg takes forever to plink away at a tower without Mines and Snipe only really works if he can spam it on a single tower from far away.
He works a bit better in a 5v5 where you get more chances to do things, but in the more common games, he sucks.
