Got my cleric to Anor, and feel that I had enough experience in PvP to make some personal conclusions.
First of all, Blessed weapons don't scale damage with faith very well, on top of cutting the base damage of the weapon. Until I got my Astora 1h to +6, it felt like I was using a dagger. It still does about 1/3 less damage, compared to my heavy brigand axe, on my shielder, scaled with the same 35 points in attributes. Passive healing provided by blesses weapons is negligible.
Ranged miracles are hard to hit with, same as with magic spells. Though I want to mention that Gnaw, a miracle similar to what those fat lady-priests are using, does very good bleeding damage, though I have to lay two consecutive hits, in order for bleeding to kick in. Took anything between 1/3 to 2/3 of enemies' health off. Or so it seemed... I do not exactly know how bleeding works in terms of damage.
My best PvP miracle is Lightning Stake. It does insane amount of damage, if I hit a guy directly on his head
And it seem to effect stamina as well - I am positively sure that I was able to break shield guard with it, opening the enemy for a critical.
The downsides are that it costs 50 FP and has melee range. Most useful as a surprise late battle trick - smacking an incoming enemy when we both used up few flasks
I had good fun with it, and I advise those who are using miracles to give it a try.