Why after? Isn't everything that the gargoyle gets calculated when it's summoned? Even if it isn't, a haste pot you take after you summon the gargoyle can't possibly effect it...can it?
Actually, buffs that are placed on you after the gargoyle is summoned do in fact effect it too. That's why the highest DPS parses you'll see will usually include something along the lines of; " I popped Gargoyal when I had Mirror/Greatness etc and heroism was about to go up."