I was playing a season 3 barbarian and I noticed that with the blood boiling aspect imprinted, during combat, time is passing by and all of the sudden the blood boiling aspect shows my next skill will overpower. It’s too late…my basic skill has overpowered and not the skill I wanted to overpower. It would be beneficial, as for me, if it showed a seconds counter so I will be ready to use the skill that I want to overpower. Skills like barbarian’s ‘Bash’ upgraded to ‘Combat Bash’ and the Aspect of Sundered Ground show a counter so you know when to use your next skill for overpower.
You just made me realize, OP should be just a proc. that depends on your build & stats (without being relevant which skill did it) 
Pay more attention maybe?
Try a build that doesn’t use a basic skill. Whirlwind HOTA for example. Or use earthstriker as your main overpower generator so you can get more guaranteed procs on core skills.