I'm 99.9% willing to say I never got close enough to use the main attack of the riot ships and kept them about 10,000 out to just plink away and kill engines. Regardless, their engine killing as is seems basically useless compared to other ships that can actually reduce things to 0 and it appears the only thing people even want them for anymore is the tazer module?
I don't know about that. If I can get a large number of ships to 1/4 speed, or even 1/3 speed, that seems really useful. Not only on the defense, but also on the offense.
Riots are great at severely reducing the engine health of a large number of ships, and stay far away from them in the mean time. Sure, other things that can take them all the way to 0, but can they zap the engines of the number of ships that riots can in the same amount of time for the same cost efficiency?
I will concede that when there are only a few ships with high engine health (not a rare case nowadays), the riot control starship is not the right tool for the job.
(BTW, despite my defense of the riot control starship, the modules could use an engine damage buff, higher mark modules could use some better growth with engine damage and/or number of shots, and the base ship could use a HP buff)