As long as you keep Saboteur Poison II and Bio III on, you only need to deal 3166 damage every 8:20(merited convert cycle) to stay even with his regen. Any additional damage is net gain on your end.
For a BLU to counteract Kirin's regen, using Disseverment for 22hp/tick you'd have to deal 5600 damage every 10 minutes. BLU stands to gain 1500+ in refresh every 10 minutes. So you'd need to safely(not wasting much on self-cures) use that 1500mp to deal more than 5600 damage over a 10 minute period. A better way to look at it might be 560 damage every 1 minute period, gaining 150mp in that time. If 2 Cannonballs deal more than 560 damage, you could easily take out Kirin. Walking in during Stone and Quake to reuse Disseverment.