Glacial Path

The cooldown is fine or even too low given how powerful this ability is. You can't just use it to poke or waveclear in the early game. Why would you waste it like that? It is your tool to engage or avoid getting ganked.

Lissandra has other issues.

zeds w has the same cooldown, when you have no cdr and only 1 point in it. while lissandras e is slower it deal damage and has more range, i think its a good trade off, once you have cdr the cooldown doesn't really even matter

lissandra does need some work but her cooldowns aren't the issue

Objectively (meaning, ignoring her other glaring problems, like a lack of passive), I think it's actually balanced quite well. They didn't want her, as a control mage, to be too oppressive in lane or be able to freely escape any gank while in lane. Remember that she and Azir are the only mages that have any sort of dash/blink (except Ahri, which is more of an assassin and still it's on her ult)... and we can see where Azir ended because of "balancing problems".

So they balanced it by giving it a very high CD early, where she has to max her Q. Afterwards, it decreases 3sec per level, leaving it at exactly half the original cooldown when maxed.

Considering she's a who can slow and root entire teams, making her already hard to gank and kill?

No, not really.

It has such a long cooldown because of how powerful the ability is.

It's not a dash it's a blink so Lissandra can escape pretty much anything as long as she isn't cc'd so Jarvan and Veigar's cages etc aren't a problem for her, I think the only thing she can't escape is Camille's ult

It's also her most damaging basic ability

Considering Lissandra is a champion whom you can't really interact with at all unless you're a poke mage with some CC, I'd much rather have her Ring of Frost have that 24 second cooldown, but I don't think she needs lower cooldowns at all.

her early game and laning phase is really bad due to her long cooldows. it gets better as you gain levels and some cdr, but I agree, 24 sec is too much for an ability that can easily be interrupted or played around.