Mech blockhorn 

Mech Mimicker because it can use its ability to mimic blockhorn and easily defeat it. It can also use it's speed to doge blockhorns attacks and get behind the barriers that blockhorn makes. 

I'd say blockhorn.

I've never used either, being f2p, but from what I know and have seen blockhorn is generally better, and fits with the current meta more.

I wouldn't say 'eaisly' cuz it's only a tiny shield it gets.

Blockhorn with storms will kill the mimicker from full hp anyway. 

Well I don't have much experience with mimicker or blockhorn so I thought that it would work. :) 

I got a feeling that death walker trumps both of em. Just a feeling.

Mimicker if you like scouts, Blockhorn if you prefer tanks. Overall, Blockhorn is better thanks to the HP and shield.