The skill reads like:
Life leech affects Force Shield instead of Health

It works fine, as long as you do not have full force shield.
If you do have full force shield and deal damage, it resets your force shield to 0 and immediate starts the passive regeneration, ending up with full Force shield after ~0.5 seconds or however long it takes.

it means you get effectively squishier with that node. Especially if one wants to combine this with abyssal shaper - masochistic effigy (doubles max force shield, but reduces max health to 5% of max force shield),