At some point BT > MS, for DPS. It depends on your gear and spec of course.
What you end up doing is forgoing imp berserker stance, precision and rampage if you choose to go MS. Now precision isn't nearly as useful for a 2h war, but if you have less than 8.6% chance to hit, you need to get that.
MS with not-completely-epicced gear, will usually out damage BT. Even without imp berserker stance, precision and rampage; for 2h.
The hp regen on BT is not what you get the ability for. BT converts 45% of your AP directly into damage every time you use it. No other ability (besides victory rush, but that's very situational) gives you this much damage per AP.
Depending on your gear, and weapon. When BT outdamages MS is simple.
MS damage for a 2h;
(Weapon Damage {Pre AP}) + (Mortal Strike Damage Bonus {210 at 70}) + (AP * 3.3 / 14)
If this is equal to or more than BT damage;
AP * 45%
Then MS > BT, otherwise BT > MS.
Simple comparison and example;
Shaarde the Greater equipped on a warrior with 1500 AP, and is level 70.
205 - 309 base weapon damage
+ 210
+ (1500 * 3.3 / 14) or 353.6
-------------------
768.6 - 872.6 damage from MS
BT = 1500 * 45% = 675 damage from BT
So...
Merciless Gladiator's Greatsword equiped on a warrior with 2500 AP, and is 70
365 - 549 base damage
+ 210
+ (2500 * 3.3 / 14) or 589.3
-------------------
1164.3 - 1348.3 damage from MS
BT = 1125
You can see that BT is catching up, even though we substituted a much higher DPS and slower weapon. But that it does indeed take a stupid amount of AP to make it worth more than MS.