It's clearly an exploit but the closest-thing-to-an-official response so far is they're Looking Into It™.

http://forums.elderscrollsonline.com/discussion/comment/708164/#Comment_708164

TheBull wrote: »

What do you guys think? To me, it seems to be throwing things out of whack.

Animation cancelling is the result of an intentional execution priority existing among the abilities (as well as some unintended bugs).

There are/were some unintended consequences that ZoS intends to address.

As far as I know, that's about it. Other than what has been patched already, I don't think ZoS has said what the unintended consequences are, or what elements are bugged, or what kind of game balance they are shooting for.

So while I think it is highly unlikely that the system will continue to stand as is, it's not really possible to gauge what changes will be made.

Fundamentally the oddities in the current game play seems to be the result:
- a system that depends on animation duration and resource cost for balance
- bugs/unintended ability synergies that violate the above in a variety of instances
- a flawed implementation of per hit procs and AoE's multi-hit abilities.

These aren't simple issues. They will probably be addressed over more than a couple of patches. I think we will have a better idea of the intended game play direction in a few weeks as this is likely something that will be addressed along with class imbalance.