Makes sense, since the reasons you dislike it (most of them) are the exact same reasons I like it. I was taught in the thought-school that the best form of healing was pre-emptive - until you got to Heal, it was usually a better use of actions/resources to kill the bad guys faster and heal afterwards than to try and play HP ping-pong with monster attacks and Cure spells. For that school of party-building (in 4E lingo, a full party of strikers/controllers, playing for alpha-strike tactics), Lesser Vigor was a thing of beauty and wonder.
Your flavor-related arguments about it being infernal magic are spot-on, though. I like to think that, despite lack of any explicit mention in the rules, consuming/using devil's blood on a regular basis as part of healing has got to result in some unpleasant side effects.