I think that's the point people are trying to make. You can't quantify these effects, really, with a spreadsheet so you'd have to have someone running firebomb that also has a flayer which is a pretty rare weapon. On top of that he only posted that he got a flayer with a link to d3 website. No info about his current gear, how his flayer rolled, etc. How are we supposed to help him?
Even without a socket, without gems, you can get a good idea of what rain of toads does with and without a flayer and make a decision yourself. But if the original question is basically "is firebats better with my current weapon or should I switch to flayer w/ plague of toads" with no additional information, how the hell should we know!?
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Anyway, I have this flayer:
http://us.battle.net/d3/en/profile/eek-1673/hero/2760823
and yes PoT is good as long as you have the gear to back it up. Straight firebats/vampire bats is better for solo though but in a group fire/poison is decent (especially with addling toads). I couldn't tell him whether or not he should use it without seeing his gear or the weapon roll though because the weapon could be garbage. I mean I'm using the flayer just for its base stats right now so another leg could be much better if it rolled the right way.