Well, Marina is a lot like Nistarok. Sure, the thgh star damage reducers are really flexible as they can both block damage and deal damage, but using the 4-5 stars as damage reducers is like treating them like a 2 star, as you could get the same damage reducing effect using a good 2 star. Using it to attack would be decent, but the 5 Damage isn't really so good, and will not open up for 2HKO's. Also, using him to attack would compleatly waste his ability.
Striker, however, is used only to attack and is really deadly. It goes through any blockers using SoA, and can deal 8 damage with fury, witch opens up for various 2HKO's. Practually, he's stronger.
Also, +2 power and -2 power is the same. Let's say that it is Striker vs Striker, one of them with bonus. Both put 6 pills. One of them would take 24 and one 36. It would be a 50% Power difference. Now, imagine what it would be like if Striker would be a Banger, once again 1 with bonus and one without. this would result in 48 vs 36 damage if both players put 5 pills. Once again, 50% difference. The difference is that +2 power would be more useful if you pill, and -2 power more useful if your opponent pills. For example, you would see a difference if he'd put 8 pills and you would put 2 (you have bonus). It would be 32 vs 18. Now, if it would be +2 power, it would be 54 vs 24, a way higher difference than 32 vs 18.
So, if both players put equal pills, it's the same. If the player with bonus put less, -2 is better and vv.
The thing about SOA abilities is that there's often one ability you REALLY want to stop, and a couple you don't mind stopping, and one card that doesn't care at all. (Say Copper, Lehane, Dayton, Aurelia)
You're rarely ever going to stop the ability you really want to, whereas with DR it's almost always useful whether it be reducing damage or preventing a fury win from a low damage high-powered card like Lehane.
it is different
many people said - power is better than + power
lets say I use striker against aginst rubie (no uppers bonus)
and you use lucia against rubie
striker VS rubie
6 power vs 3 power
lucia VS rubie
8 power vs 5 power
striker 2 pillz (18 attacks), rubie needs 5 pillz (18 attacks)
but +power is more useful if you against +/- attack clan (because less pillz needed to match up with their +/- attack bonus)
lucia 2 pillz (24), rubie needs 4 pillz (25 attack)