Yes, kensai is more damage than half-elf.
Half-elf dilettante has to generate 2 points of damage and 1 point increased critical weapon threat per hit to match kensai. Show me how that occurs in sustained, non-situational combat. It doesn't.
Normal elf is better than half-elf because of the elven bow enhancement line that gives +2 to hit and to damage. Again, half-elf dilettantes don't give that on a sustainable basis.