Either you have no fucking clue about raiding or you're biased as fuck.
Healthstones are irrelevant for any serious content because they share a cooldown with health potions and heal slightly less. Combat rez is typically not worth considering for raiding either because the chances of not having any druids/DKs is basically zero. Gateway can be useful but it's situational and there's no reason to bring more than one of. The latter two are pretty akin to time warp in that there's no point in bringing more than one warlock for them. Damage cooldowns are strictly inferior to those that mages have. Absorbs can be very useful but often end up just absorbing damage that mages don't take to begin with (better mobility & ice block). Non cooldown based self heal drops your DPS into the gutter for 2/3 specs. For the latter two you'd also have to take into account life tap which counteracts the sustain to some degree depending on the spec.
When it comes to taking more than one of a class to a raid, mages' ice block alone provides more utility than everything a warlock has combined. Having as many immunity cooldowns as possible makes a lot of encounters (including the hardest EN boss, cenarius, and the probably hardest ToV boss, helya) a lot easier.