uhh they can actually take a pretty big beating
i played jayce in lane vs a heimer last night and it took me 2 Qs or an E+Q to kill a turret, and that's a lot of burst that i wasn't able to use on other targets for a pretty long cooldown and at a pretty high mana cost
and my W triple shot wouldn't even kill a turret until i finished my manamune... but i guess that's just the downside of a tear build.
and if you're talking about lategame teamfights... spread them out so that they don't all die to a single aoe. or stockpile them since they can be placed pretty reactively anyways.
Well ther are better charcters to play against Heimer than Jayce. Note that you also can auto attack them.
They also have a cooldown of 24 / 23 / 22 / 21 / 20, which is MUCH, MUCH more than most abilities take which can destroy them.
(Also note that you can't have several turret stacks until you reach a certain skill level in your Q) So "simply gather stack", is easier said than done.
Especially if you have a 20s+ cooldown and they die with 2 AAs or 1 skill)
P.S: Even if they're not stockpiled there are man large AoEs which easily destroy them (even a support Zyra ultimate...)