I tested Slaariel's changes like a year ago when he wanted to correct Eisley's shit. He based the procs off of a 1.5 or 2.0 delay or something, iirc. He tested with me against a level 65 mob simulating Book 1 and Book 4 and they were pretty decent-looking. But this is like a year ago's recollection. Maybe something got changed since then.
I know this thread is over 2 and a half years old at this point but Form of the River Keeper proc is still busted.
Not sure if this was ever looked into by a dev but the following are my experiences the last few months:
Back in November 2017 after getting my mosquito spear out of Abyss I parsed a few hundred mobs while in bear form with JB, GoE, Stats, Relic Focus, Raego, no blood feast tomes done. Results while in bear form without divine rage up showed a maul proc rate of 1%. Results in bear form with divine rage up resulted in zero maul procs. Yes, zero.
Fast forward to the recent patch that buffed scourge of life, plague wind and supposedly upped the proc rate on maul proc. I got excited at the thought that bear form might be fixed and did another round of parsing. Same buffs as last time but now with Blood Feast 1 completed. Ugh, disappointment. Now maul does not proc at all with or without divine rage. Not a single proc.
Bad luck? Noob that doesn't know how to parse? Ehh, maybe but not likely.
Please fix this devs, I beg of you. Form of the River Keeper was one of the spells I looked forward to most while leveling up my shaman. I wanted to be "The melee shaman". Not sure what is going on with the interaction between divine rage and bear form but may be a secondary thing to look into.
BTW, thanks for the DoT buffs, those are awesome! But I still want my maul procs!