It's the Thrall and Aggra of MoP.
Wholly uneeded, unwanted, and won't really put any positive influence on the story.
The Thrall and Aggra of MoP is...Thrall and Aggra. Neither Jaina nor Kalec resemble these two in any way. Jaina is a wounded character and considerably darker now than before. No Green Jesus here. Push her hard enough and terrible things can happen.
And Kalec, a former Aspect of Magic is just on a totally different power level than Aggra. Aggra never stood a chance paired up with Green Jesus. I'm glad that Jaina has a consort who is a peer to her, not merely arm candy.
Kalec, too, has his sorrows. He is also genuinely likable, unlike the wildly irritating Aggra.
It's not about the characters resembling each other. It's the relationship itself.
Thrall and Aggra's relationship wasn't needed. Anything Aggra did in Cataclysm, would have been much better filled by Muln Earthfury and Nobundo (For example, being the ones to piece Thrall back together, without the lovey dovey stuff). The relationship, to me at least, felt very forced - In The Shattering
, Aggra was a wonderful character who I could have seen being with Thrall, but in time. Aggra was almost stereotypically feminist, having a very strong 'I don't need no man' attitude. This was a good part of her character, she was almost playing WC3 Tyrande to Thrall's Malfurion.
Come MoP - She's like Tyrande in WoW. She is completely reliant on "Go'el," hardly thinks of anything other than him, and worst of all - She went from feeling like, "Go'el, you aren't so bad after all," to, "Go'el, I love you forever and want your babies."
Jaina and Kalecgos, now, throws it into a completely different ballpark. Like Aggra, Kalecgos was integral to Jaina's growing as a character - This is perfectly fine! But, never mind the fact that he's a dragon and she's a human, this romance between them has done nothing that just being good or best friends couldn't solve. And, the worst part of it is, Kalecgos hasn't appeared at all yet in MoP, not even next patch (So we've seen). This makes the relationship feel even more unnecessary because it's not doing anything more in the story - At least Thrall and Aggra had Elemental Bonds, as contrived and forced as it might have been, but Jaina and Kalecgos have nothing like that so far. And no real sign of having anymore time together, either.