I like the idea and design of this set and would like to use it, but in the end it's too restrictive, too conditional, and has too many of its functions negatively affected by mechanics introduced after it was introduced into the game. When Malubeth came into the game, long before 1.6, health was a desirable attribute and Battlespirit did not hit doubly nerf skills/abilities that both heal and damage by 50%. During the PTS process for the Imperial City, ZoS recognized that having this 50% value applied to all aspects of a skill was too damaging. It wisely made it so the 50% reduction applied to just one aspect of the skill and was not counted twice.
The problem was this corrective mechanics was generally only applied to class/weapon skills and not to other stuff like gear, which has caused these to be much less effective than their original intent. This set is actually hit with a triple whammy from Battlespirit. It's beam's damage is reduced by 50%. The health return, dependedant on that reduced damage, is also reduced by 50%. And the 30% bonus to healing is also reduced by 50%. The end result is that if you use this in Cyrodiil, this is what you'll pretty much get:
248 health stolen, an inconsequential amount (the very weak structured entropy skill ticks more than double this), and a highly conditional HoT that is roughly the same as a standard Mutgaen tick. Also this doesn't just automatically happen. An enemy must be within 10 meters and stay within 10 meters for this effect to take place.
For anyone who spends time in Cyrodiil, this difference between this monster set and the other "tank" set, Bloodspawn, the difference is mostly night and day. Bloodspawn also has a 6% chance to proc on damage, but does *not* require the enemy to be (or stay) within 10 meters. So all those endless fields of caltrops, 41 meter entropy DoTs, and even residual siege damage will lead to this set proccing
very often, and thus grant its user a pretty regular and nice resistance bonus and the prized 10 ultimate, numbers incidentally that are no way reduced by Battlespirit. Also, Bloodspawn's stamina regeneration is desired enough where often players just use a single piece just to acquire it.
In short, Bloodspawn will grant its user exactly what the tooltip says and do so very often and alos provide the stamina needed to "tank" damage. Meanwhile, Malubeth demands rather restrictive conditions for its same 6% proc and then see all it's values reduced by at least 50% (the health stolen doubly so) and is providing a resource that most players in this game would rather trade for something else.
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I'd really like to see Zenimax put some thought into making the lesser used Monster sets like this more relevant for how ESO is actually played. I'm pretty sure with the 1.6 changes, the designers intended tanks to desire and invest in health, but that's not how tanking has evolved: tanks are expected to contribute damage, have large resource management (especially in light with the no stamina on blocking changes), and now are finding creative ways to be ultimate generating machines - health is simply not now a priority. Generic Low health 1 piece bonuses are undesirable in light of what could be obtained with alternatives such as Molag Kena and Bloodspawn. Cyrodiil isn't played under the same rules/mechanics than when this set was introduced into the game. Battlespirit is something that has been recognized as a problem for stuff that both damages and heals, requiring specific exceptions. It would be nice to see that acknowledgement played out in gear such as Malubeth and the new Bahara's Curse set.