The mechanics of the Velhari fight aren't very demanding, but the relatively harsh gear check requires an efficient strategy. Some notes after looking at several guides:
Phase 1:
* The wowhead guide recommends having the whole raid move to a stack point for edict, which requires a lot of movement. Most other guides just suggest sharing it with the melee or several nearby people, which requires less movement but hits those players harder.
* There is a similar decision for handling annihilating strike--you can have people run it to the side, or just have people spread out enough that it only hits a few people. Fatboss claims that you can also have a tank taunt the boss near the end of the cast to force it to be cast at the tanks, which is a nice plan if it works and doesn't screw up the tank swap.
* Guides disagree on how much priority to give to the enforcer add. Some guides assign it low priority; others say it should be dead before the end of the phase in order to minimize the time spent in phase 2.
* Several guides (including wowhead's) say you should give high priority to finishing phase 1 before two minutes, when Edict overlaps with Infernal Tempest. To do this without high raid DPS output you'll need to decrease the number of healers, use heroism in this phase, and/or assign the Enforcer a very low priority. The latter two choices are probably not viable because they make phase 2 harder; the former choice is tough because Seal of Decay demands a lot of healing output. So I think it's best to pick a strategy which gives the raid a fighting chance to survive through the edict/tempest overlap. Infernal Tempest does ticking damage with a two-yard splash in addition to spawning fire circles, so a strategy which has players stacking tightly for edict won't work for this.
Phase 2:
* Fatboss considers this the hardest phase and recommends using heroism+pots at the three-minute mark (when everyone's CDs are up) to minimize time spent here.
* Some guides recommend killing the harbinger add with high priority. Others (including Fatboss) recommend putting only interrupts on it, in order to get through the phase faster. The add does get faster at casting as time goes on, but it maxes out at a 1.4-second cast.
* Some guides erroneously tell the raid to spread out this phase, not understanding that Tainted Shadows only affects the MT. Most guides recommend having two stack points in melee range, one for people with Font and one for people without it. People need to move promptly out of the font stack point when their Font debuff expires to avoid getting killed by blasts. The OT should stand with the non-font stack group to avoid taking blast damage from the MT.
Phase 3:
* All of the video guides have the same strategy for this phase: stack up on the tank side of the boss and move around the edge of the room for each Bulkwark cast. Make sure to be on the forward side of the boss so that Gavel doesn't knock you back into the despoiled ground.