I am wondering if the LOH of the player is naturally transfered to the Witch Doctor pets (patch 1.0.4). If yes, is there restriction (like a reduced proc or reduced amount), and if not, does Fierce Loyalty only transfer "Life regeneration" bonus or also "Life on hit" and "Life leech" bonuses ?
The Gargantuan has a proc coefficient of 0, which means that no on-hit effects are transfered to the Gargantuan. Blizzard has never released official information about the proc rate of the zombie dogs, but the patch notes for 1.0.4 specifically included nerfs to the proc rate for Burning Dogs and Rabid Dogs. I believe this only refers to their special abilities, however, not their basic attacks.
There is no information on whether the zombie dogs' basic attacks proc on-hit effects or not. I will try to pay attention to this next time I'm using my WD to see whether there is any proc at all for zombie dogs.
Either way, it's not really feasible to rely on attacks from your pets to proc enough life on hit to regenerate health for you.
Fierce Loyalty only effects exactly what it says in its tooltip, which is life regeneration and thorns. No other sources of healing are transferred.
Proc coefficient effects both % gained on attack and % reduction of chance of proc cc's. (I'm unclear if this is also true for critical chance and bleed chance).
I do know that rain of todd for example has a proc coefficient of .5 - and also hits 4x over its 2 second duration. Every hit has a 50% reduction to procs, therefore if you have say 20% fear on echoing fury, each of the 4 hits from RoT will have a 10% chance to fear. as far as LoH goes, proc coefficient is a straight % reduction. So if you had 100 LoH and use RoT, each of the 4 hits will heal 50 life.
Also, RoT is stackable, which means with say an atk speed of 2 per second, you could cast 4 RoT in the same location for 4 hits a second at a .5 proc coefficient. (using the previous example, that's 40% fear chance every half second, and 200 loh every half second, per enemy in the radius of RoT)