Miasma is awesome, I can tell you that since I made an A5 Miasma Merc, my life has become considerably easier
It seems like the correct proc for the build. Especially with all the -enemy resists and the fact that the build doesn't have a poison proc from it's full set bonus yet (except for the carpet of spiders on the boots).
Btw, I converted my existing paladin to a Blood pally with full Malthael set. I put miasma on the weapon but what MO's and socket fillers do you recommend? Most blessed lucky upgrades failed so my DR is on the low side, around 30%.