It's time based. The guy who said it's based off HP done to Solak is wrong. I don't think that guy knows the boss in and out like you claim he does. Saying "oh look at his hp bar and see how many clones spawn. There are actually 2 or 3 (forgot how many due not doing the boss that much lately, pretty sure 2) rotations that the manifestations spawn in. The rate is/about the same the only difference is that sometimes 2 spawn at once others 1 spawns then 1 then another 1 spawns within game ticks of each other.
Also, Duo no realms are not that risky if you have mahjarrat. Too bad I don't have that, can't compete.