Never let anything attack you without putting the creeper at their feet. That thing will severely hamper any attack and costs you nothing to keep around.
Also, most arcanes can't outDD falling petals, keep it on. (Firecombo, 3sparked attacks are exceptions.) Even against other classes it'll help a lot.
Don't spark. Waste of chi.
Don't try to outsurvive sins. They never have to lower their damage output. Wait for them to go on the offense, pop leech, barrier & growth and nuke them as hard as you can. Mystics are much, much better at spike survivability & damage than even sins. But the sin will always win on longer sustained damage.
When fighting unbuffed targets, use the mystics ability to deal very predictable high damage to bypass charms on arcane & light armor completely. Take targets to 50% hp, ish, and nuke arcanes with absorb. (16-17k is enough to kill without a tick.) For light armor pop the guaranteed crit buff, leech the mistress, use extreme poison & hit them with your lvl100 attack skill. (Name escapes me atm.) It'll hit them between 15 and 30k, for most light armor it'll bypass charm at 50%ish.