I agree with many people here claiming that Reg is hard to play and if you have a teammate that can´t play him, it gets really hard, since he feeds the enemy often.
On the other hand Reg can be a very important supporting character! I always play supporting and going into melee if my partner has a UB or Oak (or Rook). Important is to be mobile all the time, always being out of range of teleport from erebus f.e., but always i nrange of hitting / supporting the enemy. And at last you get a fleeing, low HP enemy with a good map control (watching which one is low on HP etc.).
I love that DG and played alot with quite good people lately, improving my game alot. I would say it´s unfair to change teams if someone chose reg. That´s the problem almost seeing always the same DG playing. Boring!
I vote Reg: thumb up if played wisely and with a bit foreseeing.
F.e. early game you can force the enemy to leave lanes if shooting at him permanently, keeping his HP low ! Just a matter of gameplay.....