I went through the first intellect devourer fight and as a DM I think this fight is a bit out of line. The player has two characters who will have around 8-10 HP on the average and the IDs will do enough to kill one of them in two blows. Ranged fire is unreliable, I generally do no more than 3 points of damage with a bow. I beat the fight by running a cleric alongside Blackheart with both using shield of faith and guiding bolt, options that I think surpass what most characters have available at that point in the game.
I think the idea is to avoid them by taking high ground and staying out of melee distance. You can try sneaking past them. In terms of RP, since you first saw them and they scattered you could justify prepping yourselves for the fight with bless etc. Utilizing the mechanics of the game such as dipping weapons into fire, using ranged attacks, hopefully if you had a bow and also taking high ground which is conveniently provided to the right. If you choose to get upclose for attacks that is your decision, but if you dont have a fighter or barbarian that wouldnt make much sense. Therefore the only option would be to go up high and travel to the far end of the platform while using ranged attacks. It makes the most sense RP wise to utilize this strategy and by doing so I have never been touched by those creatures. In terms of a D&D setting it would also be effective however if you threw an unseasoned low level adventurer in that situation maybe they wouldnt take the same tactical measures. Although these characters you control are clearly experienced adventurers even though they are only level 1. So I disagree with you.
