Sanctuary Onslaught and Elite Sanctuary Onslaught are much faster, if you have someone carrying or you use a good subsumed ability.
Doing an exterminate with a frame that can put enemies to sleep is also decently fast if you use the stealth mastery multiplier, although the weapon you want to level needs to be able to oneshot enemies, so go for lower levels. Some others option if you just want to level your frame are a huge aoe weapon and Banshee's silence, or skiajati and stealth finishers.
Helene, Saturn should also be good. Its lower level than Hydron, but same map and drops orokin cells on occasion.