I'm probably going to agree that UB stepped into a vat of nerf for beta 2. First DG I played, and only way that he was playable was through massive speed upgrades and warpstone. Even then it was rather difficult to challenge other similar players, to the point that I rarely got kills.
The only useful way to play UB in my experience is to use him as a fast melee disruption to support a kill by another dg (especially with the foul grasp stun, but that comes so late and doesn't do enough damage). With a couple of speed boosts and a warpstone, UB can tele in and provide a bit of chaos/disruption while another dg deals a death blow. Erebus, however, can use this tactic as well and do it much more effectively.
Most of the UB's powers focus on improving his basic attack, which can easily be mitigated by stacking up on armor - I've been able to go straight melee against a UB a few levels higher than me and win fairly easily, without much recourse, especially with DGs with ranged attacks. And the DGs without ranged attacks are built to be more powerful and will usually win (Rook/Oak).
Have only been playing since Beta 2, but those are off the top of my head.