All stars are pretty well rounded offensively and defensively. you have cards like ashley and marina for D, and cards like oyoh, eyrton, randy , robb and lamar cr for offense. Then you got striker and alexei as your ability stoppers and can also be played offensively. then there is jessie who I mainly use as an anti damage reduction card. as far as hammer goes, I find his power too low, I usually use striker, marina, oyoh or eyrton instead. if I'm looking for big damage then lamar cr is obviously a better choice, same power, he has SOB and he has 8 dmg without courage giving me more options. eyrik as a leader is good for all stars but in some cases it can be better to use 1 of their 5 stars in place of a leader. It comes down to what cards you own, personal preference and strategy. If playing in Survivor T2 then I would definately use eyrik.
Eh, they are kinda both. They got some good defense with DR's and SOA's, but their bonus makes them good offensively.
And as a monoclan, Eyrik is definitely good. His reduction goes first and then the All stars bonus kicks in