Before you dive into these, I want you to keep one thing in mind. These are guides, they are designed to give you an idea and to give you tips on what to do. You'll find elements here that you may or may not agree with, but for the most part this is what I use.
Some info about me: I have done every vet trial and every HM (the only exception is vAS). I've off tanked and main tanked all of them and have pushed some decent scores over the last few months or so. The builds/set ups I use are for the super end game. If you are in a guild/group still learning or still progressing and these guides don't answer or help you please let me know.
Instead of giving a wall of text here's guides specific to each trial and each role that a tank could do.
Generic Build, used for just anything overall
vHRC [HM and non HM]
vAA Main Tank
vAA Off Tank
vSO [HM + non HM]
vMoL Main Tank [HM + non HM]
vMoL Off Tank [HM + non HM]
vHoF [HM + non HM]
These won't explain much, but that's sort of the point. If you see something that doesn't make sense, you ask. Makes it easier for me to give proper help rather than a generic wall of text that answers maybe 1/3 of what you're looking for.