Quote from Drizzit;868494:
Apparently nobody else knows how to do Iroh's redirect lightning trick.
It's easier to redirect lightning when you're redirecting it from a bender who threw it at you. The stuff is so potent and hard to control that it's basically one big telegraph. It's also very linear unlike air, traditional water (not ice), and traditional fire (not lightning). But redirecting a current of electricity through a wire, something that travels faster than you can react to it, the timing required for catching and channeling that current would be beyond precise, not to mention that said redirection operates under the assumption that the flow of electricity doesn't last long. Iroh may have created the ability, but even he pointed out how dangerous it is to even attempt redirecting lightning. Sustaining that redirection for more than an instant to a few seconds doesn't sound very feasible for a bender.
@Kueh:
[SPOILER="Spoiler"]
Toph was the originator of metal bending, but she in her life (and she was only 11 or 12 when she learned to bend metal) could never bend platinum, she who had one of the strongest dispositions to bending earth and metal. She was a master of these two things, with her only weak point being the largely reduced ability to bend sand, which was because of the way she interacts with earth and not because she simply didn't have the talent for it. I'm going to give the benefit of the doubt here and say that there are simply some things that just cannot be bent no matter what domain they fall under.
Lin didn't do damage to the entire chassis, only the glass parts. The metal remained intact, with no dents or scratches to be seen.[/SPOILER]
@The Cat:
[SPOILER="Spoiler"]I couldn't even call what firebending did to those mechs effective. It pushed them back, sure. The only thing to even be phased by the pushes was the pilot inside, and that was the equivalent of a nasty speed bump. The mechs themselves were largely unharmed (if at all), and only mildly inconvenienced by knockbacks. What's more, Korra and Tenzen were clearly overexerting themselves in that battle. Sure, they were shoving the mech around, but it was taking a huge toll on them just to keep the thing at bay. The mech, however, only continued to reveal more and more nasty tricks up its sleeve.[/SPOILER]