I wouldnt rely solely on thrust, as it has a tendency to "miss" as it is slow, and if the enemy isnt lined up correctly, it can cost you (having to repeat the combo sequence again since thrust was your trump card)
id spread em out equally, as thats my playing style (only have two on each combo skill though, but dealing around 1500-1800 damage per combo on the monkey, and a fully maxxed blade fury does roughly equal damage) thats around 3000+ dmg for a 12 hit combo
so im average i suppose, not excelling at any one move, but if i screw up, hey, no big deal,
I would however like to know how much damage a certain combo sequence maxxed COULD do though, such as flourish, or thrust like you mentioned, just I wouldnt max the lower ranked ones i guess.