In the first Rank i always go Spiritwalker's Grace, because let's face it it's Rehgar's primary and most usable spell in the game, so reducing its mana cost means you get more of that awesome healing.

To be honest many would choose Feral heart. Me, i am choosing chain reaction because i try to focus a lot more on the survivability of my teammates rather than my own. My death < Their deaths ( I M H O ). For this reason i focus more on the shielded ones and well let's face it at 16 i am getting a hellstorm of self heal thanks to my 5th rank choice.

It's by far the best possible choice when you assume the role of the true supportive player and you make sure your initiators get some suppresive fire which is cool /or/ your assassins(that are being hunt down) won't be chased for long before gaining enough time to counterkill the chasers.

LET'S ****ING FACE IT. WHEN YOU GO HEALING SPEC THAT ULTY IS SAVING THE MOST PINNED DOWN ALLY'S *** AND YOU MAKE SURE THE OTHERS SURVIVE WITH THE SHIELD-CHAIN HEAL COMBO. IT'S PRETTY MUCH THE REASON EVERYONE WILL BE THANKING YOU THE ENTIRE GAME.

Again, it's your primary spell and you will be wanting to be casting a lot and to be affecting as many heroes as possible.

It's enough suppresive fire by both beacons(exp. heroes) and you can assist in the taking of the camps so that's also a good think since let's face it not many specialists are that good at their job.

This is pretty much player's choice. For me storm shield gives me 3 precious seconds in a teamfight to better place your totem and heal. 2nd level ancestral healing is also pretty good. And if things get desperate you could always pick Rewind

Thanks for checking out my guide and i hope you enjoy the game ! :-D