The reason is that at low levels you dont get (1) level bonus on dot dmg, and (2) instrument bonus on dot dmg. At lev 31 or whenever you get your first dot, you would be lucky to get 30-40 dmg a tic with one song (with a GOOD drum), but later on we get 4 dots that do i think 44 dmg un-modded. With IM3 and a TDoK my dot dmg is about 142 ish. Mind you this is just what I can remember off the top of my head, but with a little more work on aa's i could pass 100dps with just songs. Also, those first dots do much less damage than the higher level ones. I.E. tuyens chant of fire as opposed to tuyens chant of flame.