Just gonna go ahead and tell you what I've found, playing Ninja so far.

By what I've gathered Lotus Kicks % chance of performing a dash attack can proc per enemy that you land the initial attack on. It makes it a great zerg clearer and even builds up your Ninja Charge Bar pretty damn quickly.

If you want to rush through the first "introduction" mission then just grab that, group up all the mobs and it should destroy them all pretty much. Having them all bunched up is key to this though.

Due to the way the Ninja Charge Bar works I've been grabbing items that inflict Physical damage over time. When the bar is charged you're constantly stacking those bleeds which just melts away at the big mobs. (Life on hit would also work amazingly to save on potions).

DON'T UNDERESTIMATE THE KUNAI DAGGERS. From afar they're pretty lackluster but when you're in someones face with your Ninja Charge Bar full they destroy single mobs.

At level 6 I've taken on about 2-3 golds and 3 purples and a bunch of trash at the same time (Synergies Realm of Discord).

Whilst dragon breath seems good its pretty useless and unreliable, I really wouldnt pick this up. They should probably change the ability to an arc of fire rather than moving balls.

Get a point in Body Flicker as soon as you can, the damage reduction, damage to secondary targets and attack speed increase is crazy good. Especially just for having one point in it.

Put a point in Thunder Clap just for that early leap, useful for getting out of tight spots although the aiming feels a little weird.

Hope this helped somewhat.

Still a low level but I've re-rolled a bunch on this Ninja (Playing Hardcore Elite)