At level 6, with Glass Cannon (6 AP), Guerrilla (+25% in sneak), Ranged 5 (+25%), Finesse 20 (+50%), Huntsman 1 (+5% high ground), Flesh Sacrifice (+20%), and Snipe(+100% in sneak) I do roughly 150 physical damage to Alexandar outside of combat. Once I'm in combat,
I'm not sure how the bonuses are calculated. Snipe does 56-61 dmg after applying Flesh Sacrifice and I end up doing about 150 physical on average, in sneak, with high ground and 25-27 dmg crossbow.
This is before the battle starts. When it does start, I am too far away to take damage. Once it's my turn, with Glass Cannon I can use 1AP to Teleport the target back to low ground and out of line of sight, Get 1AP back with Flesh Sacrifice, Use 1AP to enter Sneak, 3AP for Basic Attack
that does about 65 dmg, Get 2AP back with Adrenaline, 3AP for second basic attack, 2AP for Walk in the Shadows, then go into sneak and wait out your cooldowns, and by the time Invis runs out you are already in sneak and you can use Snipe again. So, I can do abut physical 280 dmg, hide, and do it all over again.
With this strategy surfaces were never a problem for me as a ranged character.