found a useful champ to abuse garen with

toplane ap brusier

insert ap item here + take w level 1 vs him and trade alot.

im not gudd at this game but seems gragas really abuses him in lane, also helps negate his ult magic damage, and gives better heals on his passive, but if its an ad team i wouldnt build it.

i will say this though, garens passive is bs, not because it heals, but because its like 2 seconds after taking damage its up.