Legion rewards blocking mark icon

My build has perfectly reserved mana and mana regeneration with spell echo and not yet high enough cast speed which means I not only have to hold smite and hope 95% hit chance doesn't make me miss twice but also I have to hold sniper's mark button long enough because if I don't the game will forget I've ever pressed the button and my character continues to cast the spell that I'm holding with RMB.

Now this is a big issue because on Ornate or Mystery reward I simply cannot see If I have marked the target and looking for some slight green glow while the target is frozen and has myriad of other glowing buffs is simply impossible in this game that is littered with indistinguishable effects.