Okay, latest build has this change:
now converts up to 60 Rage into up to (((AP * AP) * 186) / 10,000,000 + 47000% of AP / 10,000) health.
What this translates to, if this is the 'working as intended' version, is that Frenzied Regeneration is now pretty much useless. It -used- to start at a base heal of 32K, and with Vengance proc'd heal for 50 K and crit for 90K. Now I agree that healing for 30% of your health (mine is 262K right now) every 12 seconds or so is a bit overpowered, but there are nerfs, and there are 'why do I even have this skill' nerfs. Current version shows a tooltip of: "Heals for up to 2,279 with 60 rage." Not a typo. Hopefully a bug. Because when you get your max stack of Vengance, it heals for 21,763. In other words, 'it starts by healing 1% of my health and gets up to healing less than 10 % of my health. That's LESS than casting Healing Touch (30,838) on myself. Except I can't cast it on myself without popping out of bear form.
I didn't notice it until after I ran the same dungeon with a full five man that I ran before this patch and was able to heal through the second part of the first boss mechanic and was wondering why the healer was having trouble keeping me up from so much magic damage flying around. If it wasn't for the fact I had a monk healing me, I don't know that I could have gotten through the instance, because -he- was having trouble. I've been used to using it as a 'hm, healer's falling behind, here, I'll help top myself off', but pretty much at this point it's pointless - when outdoor, non-elite quest packs can hit me faster than I can heal myself (Leader of the Pack heals for 10K, by the way) while soloing a normal quest chain, something is Very Off.
Also, Vengance seems to have gone back to its old formula of '5% of damage as AP', because now that I'm watching it with my spellbook open as mobs hit me, it ticks up -very- slowly (and my FR heals go up very slowly as a result). After chainpulling 12 mobs across a field, I had half of a Vengance stack (11K AP bonus) so I was healing myself for 10K and change health, and then doing the 'let's fight the big bad at the end of the quest line with the name NPC, the mob was hitting me for 9.6 K every 2.5 seconds and I could only heal myself for 20K every time I got up to 60 Rage. So it was slooowly whittling me down -- and this was a solo quest mob. :|
Other observations: applying Mark of the Wild increases the value, but putting on +609 and +510 stamina trinkets does not increase the heals. However, taking off gear with stam decreases the value -- I'm not sure if I'm needing to break a threshold of some sort to increase the value or if only Pandaria gear increases your FR value. I haven't found stam trinket yet in MoP to prove this one way or another.