^That's just a dumb argument, plain and simple. Their typing's synergise well, as you seem to half-admit. The only actual objection you raised is that Hail impinges Gliscor's ability to recover. By 6%. And Hail will only commonly be up if we go directly from Aboma to Gliscor, in which case, we'll be facing something which we can actually beat and SubPass on. Having the full 12% recovery is worthless unless Gliscor is in against something it can beat. Even with Hail up, it barely hurts Gliscor's ability to stall because the Hail will hurt the opponents pokemon more than Gliscor even if they carry Leftovers.
Finally, like bubbly said Abomasnow isn't a crappy pokemon at all, it has quite a few niches. Considering Mamoswine is already one of our front runners, and Abomasnow has pretty much the same utility with Ice Shard (although it does narrowly miss out on the OHKO on the Therians after SR, but again Sand / Hail / LO damage all rectify that within one turn) but a lot of other advantages, I think it should be considered. If you need an example, look at ShakeItUp's old RMT (I think it was called Arcana Force or something) which used Tyranitar + Abomasnow effectively together, without requiring a spinner.
I don't half-admit it. It's true. That gives them terrible, rather than godawful, synergy. Firstly, every time aboma comes in, CBtar must come in, or else gliscor heals 6% a turn. Secondly, if we pivot directly from aboma to gliscor, as you admit, we'll have 6% healing a turn, which means he might not actually beat stuff he could otherwise, and can have massive holes punched in him he won't soon regenerate off, especially considering his purpose is to SUBPASS.
Gliscor is the point of our team. With hail down, he's basically OU gliscor, who was... rarely used in OU, for a good reason-6% healing is just not enough for a defensive pokemon, and in our case it's even worse, since he subpasses.
Edit: I'm making loads of sense. The net loss is not zero, because A:We'll already have SS down and B: If our attack already KO's, which it should, then we lose but they don't. And it definitely is. If he subs twice, with SR down and hail down, half his health is gone. Meanwhile, we don't have enough revenge-killers/fast pokemon, even with abomasnow's ice shard, on this team to just sack stuff any time because gliscor's worn down.
I see gliscor on hail all the time. It's bad. I'm coming from a place where a pokemon that is designed to take hits, lose 25% of its health, and occasionally wall threats for us has only 6% healing a turn. I see you watching this right now, and i want you to see this appear:
NO DEFENSIVE POKEMON, ESPECIALLY ONE THAT SUBS, CAN FUNCTION EFFECTIVELY WITH 6% HEALING A TURN.
Also:
Baton Pass Jolteon
Forretress
Specially defensive bronzong