Whilst I agree that 'OP' is sometimes a little subjective, and influenced by what we are on the receiving end of from AI defences... mostly 'OP' should yield to simple objective comparison of the actual numbers and functionality involved. If something is mathematically just stronger than anything else currently available, then it is 'OP'.
OP is not the same as broken: Krystenax is clearly overpowered in any simple mathematical comparison to any AoE troop - but it's not broken and doesn't ruin the game.
To your statement: rubbish. Skill in using a troop doesn't determine if it's overpowered. And in any case:
- far less than half the game's troops are really viable in the late game, let alone overpowered, whatever your skill, and
- pedantically, by definition half the population can't be 'overpowered', as 'overpowered' should mean 'significantly above normal/average power levels' - so if half the troops are that strong, they are forming the average, not way above it
End of rant. Maybe I had a stressful day too