Mez timers are tricky because different spells have the same emote upon landing and different durations. Also when someone else mezzes your triggers will fire, which you may not want.
You have two options:
1. make triggers that fire when you begin casting a spell
2. make triggers that fire from the mez landing message
The first option will fail you if mez is resisted or your cast is interrupted, and won't show which NPC has been mezzed.
The second option will be less reliable in mez duration, and will not work perfectly with multiple NPCs of the same name.
Personally on my bard I use one mez landing trigger, for AE mez only, because I have a tough time keeping things locked down otherwise. This means I occasionally get spammed with other bards using AE mez. To me it's worth it because I have wiped more than a few times due to letting AE mez drop when I wasn't paying attention.
On my enchanter I do not use any mez triggers, but they might be useful to you. I would just try it and see if you like it or not.
If you want to make some, here's a few examples (also in attached file):
*Note: If you use text to speech to warn you when mez fades, make sure you check the Interrupt Speech box, or you'll get a nice stream of "mez fading. mez fading. mez fading"
Others included in file:
Chaotic Bewildering
Search Text: ^{s} is completely confounded
Timer (1:06): Mez - {s}
Bewilder
Search Text: ^{s} stands around looking utterly confused
Timer (1:24): Mez - {s}
Deadening Wave
Search Text: ^You begin casting Deadening Wave
Timer (1:02): Deadening Wave
Stasis
Search Text: ^{s} is locked in stasis
Timer (3:26): Stasis - {s}
Perilous Bafflement
Search Text: ^You begin casting Perilous Bafflement
Timer (0:13.1): Perilous Bafflement
Bafflement
Search Text: ^You begin casting Bafflement
Timer (0:07.1): Bafflement