I find a buff unnecessary. (Cue metarage)
Guardian Angel is mostly a combo card, but not bad in mono-light, either. In fire, rage pots can make it truly wicked, and in gravity, it can keep your acceled and pulling creatures alive. In Mono-light, It is a weak, but consistent card, cheap to play, with a high HP and an anti-CC effect.
Archangel is a 7/7, costs 6
to play, and can heal.(Compare to Elite Charger, 7/5, 5
, with momentum, and Abyss crawler, 6/6, 4
, with no effect.). What part of that is UP? Plus, it still has Heal.
However, I do recognize most people rush nowadays, so maybe a small buff. What I would support is it removing poison from the target, as well. Great way to stop Plague, Aflatoxin, Infections, and stops Voodoo poison damage,(Though the poison you acquired would stay, sadly.) While still not being a huge buff that will turn it from underused to meta in a flash.