Jungler's sustain is still over the board
Jungle
, a champion having no innate healing and typically building no lifesteal, will heal for almost 8k over the course of the game, just because he is a jungler.
Is this a lot? Well, it is more than average healing done by a
, mid
or top

or
, support
, and __ almost twice as much as any of the dreaded lifesteal-tanks called ADCs will ever lifesteal__. So yeah, I'd say it's A TON.
But what is more funny is that a
will on average heal for almost a 1000 less.
How is this possible, one might ask, if Lee has in-built 30% lifesteal? Which he uses in combat with champions, while WK only heals from monsters?
Well, the answer is simple (and a bit scary at the same time): a jungler with some innate sustain is on full HP so often that they will actually waste big part of the healing provided by jungle items.
So yeah, I'd say it's a bit too much.