At the end of Act 2; it's all about 'We must go to the city. If we hurry, we can be there before the army arrives!"
Army doesn't arrive if you spend six weeks vacationing in the city. For me, they could leave it as is - if there was a segment where we intercept the army, and it gives us a reason why we can breathe and find Astarion's fangs instead.
There should be a *major* engagement with the allies you found so far - Druids, Svirneblin, Myconids, Totally-not-Githzerai, Tieflings and Harpers to rout the Absolute's Army on the march. Hells, even Gortash and his Steel Watch, it would make total sense, as he would he heralded a hero - and might paint him in a different light as for your alliance as well.
