bard heal overhealing gameplay

I was playing a game as jinx with an alistar in draft where we encountered a bard and a yasuo bot by about level 4 or so we had yasuo by about 10-20 % of his health he was running away to his turret where he then would walk over the bard heals.

The shock was that he went from that 10-20% to about 80% of his health even my support was like" woah those heals" it happened multiple times until he could just all in.

I have had plenty of games vs and with bard, although I've never played him he shouldn't heal that amount of health by level 4 o.0

if it really isn't a glitch then I'm sorry for the inconvenience. [slayer-jinx-wink]