Don't have a reference, just have tested it myself. The game has to take into account what action should go first, so that will delay the skill activation. You can test it yourself if you'd like to verify. Regardless, you really don't need to macro GCD abilities for prioritization. Just look at your hotbar or your buffs, see if you have 5 Wrath or your SC icon is lit up, and then press it if you can. Your macro also goes SC > OP > Flash, which would only activate Flash if you're completely out of TP... which isn't how you should be managing your TP unless you're speedrunning 4 man dungeons. As an example, to conserve TP, you can go SC -> CD -> Flash -> Infuriate -> SC which will use 3 GCDs, maintain AOE aggro, and use no TP while you gain the passive in-combat TP regen. Also, OP has the highest hate per 1 uncombo'd GCD, so if you ever need to grab a mob with OP while @ 5 Wrath and then IB or Unchained, you won't be able to as your macro would prioritize SC.

Also, you should be using Flash like... once, potentially twice in all of T12. You're never going to go OOM unless you need to Flash a bunch of times, which should never be needed outside of potentially a SR, and only if you've ran out of TP from OP spamming and need to keep aggro or... something. You CAN use a Mega Ether if you'd like, it just doesn't really do anything unless you're doing something wrong.