forgot to mention
this:

you can't outrun their turning speed most of the time, rocket jumping only gets you launched to your death because of the knockback, you'll never know its even there in an intense fight while its chipping your health, and even if you managed to take it down, the engi who mad it can simply plop another down in 4 seconds and gun you down. And thats not the worst part, if the engi happens to have the frontier justice....