I think I'll stay with base faith. Even if I got the heal miracle, it doesn't restore that much health.
Over lunch I took out
Spoiler
that huge wolf Sif in the Darkroot Garden on my first try. I was pretty disappointed by that whole area behind the crested door that you unlock - just a bunch of humans that are easy to beat and a crap ton of those tree monsters waiting to swarm you. Didn't bother with the Forest covenant as I've murdered all of their friends at this point. By the way - how the hell do you kill those ghosted humans? Looks like there are a ghost thief, archer, and possibly one other. I tried a transient curse but still was not able to engage them.