Well, there is the fellow "pretending to be Sammael. " That could be Taim being Taim, but it could be Be'lal mistaken for Sammael, or playing some elaborate game of his own. It's something intriguing that's mentioned a few times and then dropped, which always makes the gears turn. Implication doesn't mean much in itself; even Light loyal Aes Sedai will imply falsehood if it suits. Likewise, if seeing is believing, NOT seeing isn't disbelieving, at the Cleansing or elsewhere.

I can't see Ishy deigning to train Taim even if time permitted, but the biggest problem with him being just another Dreadlord is that the trappings of the Forsaken Taim's adopted don't square with the subservient attitude the Forsaken demand of subordinates. I guess it's possible he might have been elevated to their ranks, but if we're going to play the "they haven't said... " game, given the Forsaken contempt for contemporary channelers if he had I'd expect them to talk about little but how disgusted they were with the "new" Forsaken. I may well be wrong, but there IS reason to believe he's one of the Forsaken: He's adopted their symbolism and knows the Dark Ones command to them (not to mention his possession of one of the Seals the Forsaken strove so hard to obtain, and casual relinquishment of it to Rand as if he can take it back whenever he wants. ) All of them are accounted for when he makes his appearance to Rand, or soon after. Except Be'lal, unless we accept that Moiraines few seconds of retroactive removal were enough to make him inaccessible to the Dark One.