Torparse is definitely the way to go for tank parsing. The things I generally look at are as follows:
- APM – A low APM can often mean I was playing lazily (i.e. missing rotational cues, failing to pop cooldowns, etc). When I'm doing well on a fight, my APM is usually in the mid-30s as a shadow tank.
- DtPS – Did I stand in anything I could have avoided? Which boss abilities hit me the hardest, and are they cooldown amenable? Compared to previous runs of this boss, has my DtPS reduced proportional to the new gear I have acquired?
- HPS – Did I sustain my maximum potential HPS? What kind of overheal did I see on my self-heal? (I weigh this against whether or not the healers seemed to be having trouble to determine whether or not I should advise them to adjust their healing priorities)
- DPS – How flat is my DPS profile during burn phases? (this is an indication of how well I managed my energy) What kind of DPS was I sustaining? How well did I do on proc management? (you can see this by looking at average damage and crit % for different abilities)
- Healing Received – Weighed against DtPS and self-heal. Generally less useful, but can sometimes provide insights that I can pass along to my healers.
- Threat – Pure epeen. Doesn't actually tell me anything. Well, it's occasionally useful in progression content to identify agro drops, but that's about it.
Note that torparse is really the only parser which provides all of the above information in a format that is useful, which is why I really couldn't switch to MoX or AMR.
Regarding relics, best in slot sub-Campaign is going to be the DG proc heal and the DG proc absorb relics. Once you're mostly-Campaign (and augmented), the DR on absorb catches up with you and BiS becomes DG proc heal + WH defense. The DG activated defense relic is a good situational relic, but has inferior overall stats to the PvP relics.