Omen was the most picked agent in almost every region. According to vlr.gg, his pick rate was 98%, 95%, 95%, 96%, 95% and 90% in First Strike NA, EU, BR, KR, CIS and Japan, respectively. Brimstone, on the other hand, had 2%, 5%, 5%, 4%, 5% and 10%, in the same regions.

Obviously Omen + Brim pickrates result in 100% because team comps really need smokes (despite Liquid attempt to play without it in the past). So, in my opinion, Omen is not OP, but is clearly a better option than Brimstone, and since every team needs smokes, his pick rate is inflated.

Riot should look for buffing Brimstone, releasing a new agent that can smoke, or both. My Brimstone buff suggestion is to begin with making his animations faster, for more reactive plays.

We are in a good agent usage distribution, even Viper is being picked in a few games, Sage got back some love and people will figure how to play Skye. But it is not cool to have one agent that is a must pick, and right now Omen is a big must (with Bind being and exception).