Human Speed & Goon Pounce: You just need to combine the use of chomp and pounce/trample/etc, use the right one depending on distance to human. The pounce only fails at point blank range (when the target's bbox is touching yours) or when you land on ground before hitting. And shottied 3 times while waiting after pounce is a little exaggerated. Snipe should be used when human is further away, when you can't quickly pounce to him (or won't risk, like before running away).
Adv mara lighting: the point is making it powerful against multiple targets, not a single one.
Dretch: headshots are now 1.5x dmg (72 for dretch). It is now more difficult to kill in 2 hits. To guarantee a headshot you would need to be above (on walls/ceiling) or look waaay up from very close. I just try to stay ahead of target when possible, so I'm not chasing them, barely able to hit.
You might also want to find out if the server is using unlagged or not. Hitting a target works slightly differently with unlagged on/off.