I don't necessarily see LGB as having become a dumping ground, but there's definitely been a 'lumping together' of anything not straight. I've actually seen LGBTQQAAI used, would you believe?
Lesbian
Gay
Bisexual
Transsexual (I know)
Queer
Questioning
Asexual
Allies
Intersex
I imagine that the gay rights powers-that-be accepted any group that wanted to be included, for fear of being seen as non-inclusive. But it's too much. Have asexual people, or gay-friendly people had to fight for equality? No, not really (setting aside feminist and race issues in this context), so it's become this unwieldy thing, when really, the heart of the matter is a simple one.
Yeas ago, trans people were mostly invisible and suffering in silence, so I understand the linking with LGB. Strength in numbers, I get it, and the prejudice in the 60s and 70s was ingrained. But the world is a different place now, I think there are enough trans activists and trans awareness for there to be stand-alone trans rights groups, with one agenda. I don't see why LGB and T can't have an agreed detachment, but with ongoing, mutual support - not unquestioning support, but rather support that is fundamental, yet also able to ask difficult questions when the wishes of one group are detrimental to all or part of the other.
I suspect this lays me open to accusations of being a TERG. I'm not. I'm just a gay man who thinks that trans campaigners are at a point when they can own their fight, without hitching their cause to a vaguely-related one.