It doesn't matter if Green Goblin was on the battlefield at the time the cards were discarded
He looks like something of a beefed-up Champion of the Parish, that will buff fellow Humans when any kind of counter is placed on him
There are multiple very relevant threats which survive Lightning Bolt but die to Heat, such as [card]Yawgmoth, Thran Physician, Omnath, Locus of Creation, Crashing Footfalls, Primeval Titan, most Planeswalkers, Yorion, Sky Nomad, and the list goes on
Six mana for a couple of 1/1 snakes is pretty bad on rate, but some kind of aristocrats deck could make some good use of the ability on the back end
Combat damage is typically simultaneous, but specific card abilities may alter this standard outcome