Fleshrender rings heal 18 hp every 4 seconds, so 4 hp/ second, stack them x4 and you get 16 hp/second or 72hp / 4 seconds. Anni chest gives 52hp /4 seconds (for those classes that have regen on it. Stack them together and you get a grand total of 29 hp regen per second.
The trick is combining this with enough toughness to mitigate each hit enough to make 29 hp regen matter somewhat. This gives you really bad dps overall. The rings limits your resistances greatly though.
If you play a tank you usually have some extra hp regen options such as heal aura for chosen/knight, hp on disrupt tactics (minor like a 100 hp per disrupt), Grumble and Mutter for IB, Bolstering Anger for BG, warbellow etc for BO. Most classes have some ways to do this, combined with crafted pots, pots bought with medals and absorb pots, heal over time pots etc you can start building yourself for some solo roaming. Its fun, its challenging and most of the time you WILL be run over by the zergs cho-cho trains.
Still, worth it for that one epic 1vs1 (possibly 1vsX) where no one interferes
