Boss practice rooms

[Saccharin]

I have a feeling a lot of folks won't like this idea but here goes...

For Titan HM I have had plenty of practice for the first few phases, but I always always always die on the last phase because of the bombs. I believe if I had more practice, I could handle it, but how do you practice the last phase without a group that can consistently get there (not to mention a group who doesn't expect you to have already had said practice)?

It'd be nice to instance into a training room of sorts that will throw things at you exactly the way the boss would during a selected phase, and repeats. This way you can practice for it, and be ready when the real fight comes.

NB4 "Duty Finder"

If you can practice the boss then why would there be any point in doing the boss except as a loot piñata. Part of doing any encounter is getting it wrong and then improving and scoring that kill. If you've already mastered the boss then where's the fun.