A few panthers? Luckily you can easily build these in a competitive 1vs1...
And no, I don't think it should one-shot anything other than a bike. The 88 as prime vehicle killer doesn't do that either. If the ISU one-shots then its reload time is without relevance because you already lost the unit without having had any chance to save it. And afaik the devs said the ISU's damage in this patch is horribly broken as it just rapes tanks. (See the other ISU thread)