The sneaking tactic is especially effective if you split your party (drag their portraits apart). So a flow could go like this:
1. Sneak rogue close to the enemy, with height advantage
2. Have the rest of your party further off, also hiding
3. Have rogue (or whoever) initiate combat on an enemy
4. Sneak the rest of your party over one by one, having them each initiate combat on their own
This basically gives you 4 free attacks on the enemy. Depending on how you played it, you might wipe them all with that. Also, second the suggestions about using the environment - Larian is big on this, here's an example from early in the game:
At the first ruins you encounter, guarded by the halfling and company, there's a big rock above the two of them arguing. If you have some stealthily shoot it, it wipes out two of them - drops the number of opponents from 4, to 2. Plus, if you do it right those two won't even attack you - so you can still get another sneaky attack or two off.
