Surprize attack done right:
- The dwarf rolls there in a barrel
- The rogue sneaks there to backstab with a ballista*
- The half orc berserker throws the halfling at the enemy
* Sneak attack works with ranged or finesse weapons when you have advantage
Ballista is ranged weapon
hight is advantage
so everything is fine, but the half orc berserker has to push the ballista up the hill first.
Throwing the halfling from there gives also advantage plus surprize
I guess rolling down from a hill in a barrel counts also as advantage plus surprize

Prof. Dr. Dr. Mad S. Tist

World leading expert of artificial stupidity.
Because there are too many people who work on artificial intelligence already