At lvl 26, if you have mez resists, the mobs are probably just too high compared to you. In that situation, I would root and cast Tashani to help root stick for full duration. If necessary to mez, I would cast mez after Tashani, which lowers magic resist to help with resists.
As far as cast times of mez, if you have an instant clicky (e.g.
telescope,
goby earring, or better yet
rod of insidious glamour ), put mez in spell slot 1 and use the clicky to bypass the mez cooldown.
Some sequences that come to mind:
root/snare/long duration mez -> Calm -> memblur is useful to heal your pet. Probably not so useful until later though.
stun -> mez -> tash -> charm is a good way to recharm on break. You can also skip the stun and lead with mez. Leading with stun will only work if you have a clicky to instantly cast mez after stun, or if you have the longer duration stun spells at higher levels.
root -> tash so root sticks longer
mez -> tash -> slow
Use a clicky between each spell to reset spells' global cooldown.