This doesn't really add anything new to the conversation. The 4 piece set bonus is bugged and doesn't provide as much benefit as intended. Once it's fixed in 5.1 it will be worth more than it is now. Plan accordingly.
Also, avoid chat-speak abbreviations like "imo."
Imo 4 set is not worth it at the moment. And if it's 10% more healing from DS OR 800 mastery (~9% of DS heal as absorb) - mastery is a clear winner here.
The first reason is that abosrb is imo better then straight up heal from DS. Often we get heal split second before we DS, and straight up portion of DS healing is lost. But mastery bubble can't overheal (unless we cap it, but it's unlikely during constant boss dmg).
Second point is gearing up the team - thing that comes up most often during progression is "we need more dps" - so giving tokens for dps first will help your progression much more then 1,5% self heal increase for you.
So go for 2 set, as other people mentioned that it's pretty damn good, and don't even bother with 4 set at the moment. If they fix (or just balance?) it to be on par with other 4 set bonuses, then it will be worth it. If they don't - stick to offset pieces for imo better survi.
EDIT: About 'bursty' content - I still have a lot ahead of me in terms of progression, but so far I didn't face any content 'bursty' enough for me to change my mind about our 4 set bonus being crappy. Hardest hitting thing so far is Meng the Demented on Four Kings HC meele when he's on ~90 energy. But that can be easily managed with our cooldowns (and we have A LOT of those).