it's not as safe and easy as flesh golems before the update but at least they dont disenchant.
you can take 4-6 but anything like 8++ is dangerous. I noticed that, I always die when the 2nd batch of these hydras just appears out of nowhere.
b1m2x3 pointed out the problem in this area.
Also I tried hording all the hydras in the circle and when they got to me in the center, some hydras were stuck and clumped together, didn't do anything and the AOE dmg couldn't reach them.
after killing the inner hydras, the ones on the outer ring came in and finish me off. LOL!
I run 3 superior runes. I think 4 is dangerous due to extremely low health.
...
but then again, maybe you can take 4 and use healing hands instead.