Although that's less of an issue, it's still an issue for the amount healed. Point is, you can CC healers for a long time and nothing dies, resulting in extremely long games.
The warlock is not healing for 100K each time he goes low. It is a constant stream of low amounts of healing, and again, only on himself. While it is still way too much vs. other teams that rely on a lot of damage over time spells (meaning the warlock can greatly nullify a lot of this) it is not way as dumb as hybrid healing.
Warlock healing is over the top, but Ret Paladins not having to use WoG at all, and can use instant, free FoL that can crit for 120k seems a bit stupid.