11.5 damage is still about what you'd expect from a level 1 fighter...
2d6+6 assuming 18 Str and a greatsword. That's an average of 13 per hit.
Edit:
Let's pull out some monsters!
Air Elemental, Elder - 204 HP. AC 27. AB of +27, 2d8+6 damage per attack, 2 slams in a full round attack. DR 10/-, whirlwind form, air mastery, elemental traits.
I'm at a loss as to what Hassassin's monk would do against that. Can't stun it, can't damage it... Perhaps he could hurt its feelings by using mean words?
Black Dragon, Adult - 199 HP. AC 27. AB of +24, with lots of natural attacks.
Blue Dragon, Young adult - 189 HP. AC 26. AB of +23, with lots of natural attacks.
Copper Dragon, Young adult - 161 HP. AC 25. AB of +20, with lots of natural attacks.
Cryohydra, Ten-Headed - 108 HP. AC 20. AB of +14, 1d10+5 damage per attack, 10 attack per round. Fast healing 20, darkvision 60 ft, low light vision, scent.
Pyrohydra, Ten-Headed - same as above.
Hydra, Twelve-Headed - 129 HP. AC 22. AB of +17, 2d8+6 damage per attack, 12 attacks per round. Fast healing 22, darkvision 60 ft, low light vision, scent.
Demon, Hezrou - 138 HP. AC 23. AB of +14, bite deals 4d4+5 damage, two claws with an AB of +9 deal 1d8+2 damage each. DR 10/good, has Blasphemy as a spell like ability 3/day at CL 13.
Devil, Barbed (Hamatula) - 126 HP. AC 29. AB 18, 2d6+6 damage each, 2 attacks on a full attack. DR 10/good, barbed defense (enemies striking a barbed devil without a reach weapon take 1d8+6 points of piercing damage).
Feel free to look through the rest of that list, Hassassin this is just the top 1/3rd.