General

Ok awesome thanks guys
re-rolled my +1 atk speed and get 30% crit xD

+1 attack speed helps with only a few skills with kanna, Vanquisher's Charm not being one of them. It is a rapid-fire skill like hurricane, so I would not suggest this line for a kanna. Buff duration is not that helpful either, as most of kanna's skills last a pretty long time, with only 9-tail fury actually benefiting (and it has a long cd so it may not benefit that much).

+1 Attack Skill Target would be more useful for training.

My suggestions (considering reboot) would be %boss, %crit rate or +1 passive level skill increase for general damage. % drop is good for bossing.

I'd also suggest getting high %meso rate if you are meso farming on your kanna. I think max is +20% mesos gained.

+1attk speed lowers the delay rate of everything. i personally would keep it but all you brosk.

There are only a few lines that are worth keeping, those being % Critical Rate, +1 Attack Speed, % Boss Damage, % Cooldown Skip Chance, +1 Attack Skill Target, % Item Drop Rate and % Buff Duration.

As for which you should go for, it all depends on what you're planning to do on said character. If you don't boss on it, then a boss damage increase will be useless to you, if you train a lot, the inner ability that increases the number of targets hit with mobbing skills will benefit you greatly. Buff duration is always a benefit whenever you get it and can be used towards training, bossing or simply decreasing the need to rebuff regularly.

You should keep the +1 Attack Speed increase if you notice an attack speed increase towards your main bossing skill, Vanquisher's Charm. If there is no increase, then % Buff Duration or +1 Attack Skill Target would be my recommendations, as those two have potential both in bossing and training situations.