So this is probably actually one great advantage of a tactician over being cloak-reliant. Most fights as tactician/skaen you don't need the cloak (so far I've penciled in a few times where it's really advantageous/required to do so <water dragon, fire dragon, and maybe to only have to do the big buffing once or twice for BoW>; I might pencil in a few more), so you don't need to worry about losing brilliant because you won't actually have it during most fights - you just have it while you buff. If for some reason I need to buff again, all I have to do is Shadowing Beyond+Withdraw and that basically resets Brilliant (this is actually very important for the fights that I need the cloak, because I don't have a fire wall to self-trigger the cloak; I literally just buff a bit, stand there with a stopwatch while enemies attack me, and if I haven't triggered cloak brilliant when my timer goes off I invis, reset, buff again, rinse and repeat until I get the cloak to proc).
So I only need to be concerned for the fights where I need the brilliant from the cloak, and I need to avoid getting the tactician shaken/confused debuff from being flanked which will ordinarily dispell Brilliant, which Svef is good enough to prevent (it's not even a factor for the fire dragon fight because none of the magma oozes can actually flank me because they're ranged). (edit - not having brilliant active during a fight may contribute to tactician/skaen being slower than a bloodmage/skaen since I can't spam most abilities during fights, i'm only left with auto attack. With good timing I can do some mule kick spamming but that's about it until there's just a couple of enemies left that I can manually trigger flanked on and trigger tactician brilliant. At level 19 with my practice char now should be less of a concern since I'm hoping I can Storm of Holy Fire -> escape, brilliant, wait -> Storm of Holy Fire -> etc spam for the non-boss fights)
Not directly related, but with solo tactician, the way it interacts with charm/dominate, is that as soon as you get charm/dominated, the tactician brilliant bonus kicks in and immediately dispels the charm/dominate (verified behavior from practicing FS which features lots of charm/dominate). I guess Vela doesn't count as an "enemy" for checking who's been flanked or not.