You level to two in about 15 minutes and three in maybe 45 minutes without rushing it.
Astarion is centuries old.
I do wish the mechanics would support the narrative a bit better. It would be enough to offer a small prologue adventure just for the main PC to level to 3. And when you meet the companions they are lvl 3+, except for Astarion who you could meet later in Baldur's Gate where he'd be level 5+.
Everyone shouldn't always be exactly the same level either. Have room for some dynamics.
yup, getting to lvl 3 is fast.
astarion is centuries old. but even old elven can be lvl 1 in a DD campaign
the narrative isnt a lots out of grid : you are weak, got caught by lvl 8ilithid , seem legit. fight imp and small brain with legs, low lvl CR. then face goblin, its kinda gratuated, then gnoll, swampimp.
even in a real dd game, going to the underdark isnt that much for a low lvl character. sure. theres HIGH risk of meeting things you shoudnt. but a lvl1 drow is still lvl1 or a acid pit can be climb . as a veteran dd player, i dont find the pace too fast. getting out of the druid to search for haslin could easily take 2 or 3 game. or twice if you got some chaotic player who thinks WAY out of the box.