So much information is spread across the VP pages, so I'll try to populate this one with some useful information.
Casts Force Breath every 35 seconds. At only a -150 check, it's pretty easily resistable, especially since VP 2.0 isn't available until OoW on TLPs. No one in my six person group was hit by it.
PD also casts Healing Complete II (this heals for 20k a pop). In my 13 minute fight, he cast it eight times, but it wasn't spread out evenly.
At every 20% health dropped, adds will spawn.
80% = 2 adds
60% = 3 adds
40% = 4 adds
20% = 5 adds
I think their health does vary but it's low. My parse shows 10-50k health (all mostly named the same so parser sometimes combines and gives inaccurate results, so I think most were in the 10-20k range). The last wave had the lowest health, apparently, at 10k HP.
A 35 hsta/hagi 17k paladin with 1200+ AC took 280k damage during the 13 minute fight, resulting in a DPS of 315. She only hit me 29% of the time. Her max hit with the my gear was 1282 (so will be a bit higher with less hsta). I managed to kill PD and all of VP with one boxed group.