Rosemorn Monastary map gives 5-7k XP. That's one level. YMMV but it allows me to enter Shadowlands very deep into 6th, and I level up on the way to Moonrise or the Inn. There are several quests I do skip in Act 1, so maybe finishing Act 1 on 7th is possible.
In short - I do not think that skipping that map and entering Act 2 early in 6th lvl leaves one underleveled. In Act 2 there is a tonload of easy XP around, you rake up two levels without really noticing. Shadow Cursed Ravens are the easiest XP in the game - just
break a bottle of e.g. Alchemist Fire on your helmet
Lay'zel whinning aside the Mountain Pass map is irrelevant to the main story.
