There are no good or bad shields. It all depends on the level you're doing.

What makes owlite 'special' is that it protects from fire, a status dealt by the only T3 boss of the game, and shock, another annoying status that's also part of the Twins boss fight.

Buuuut, if we talk about general use, you wouldn't like an Owlite in a level full of freezing devilites or poisonous kats.

Elemental defense doesn't protect from statuses (fire, shock, poison ect.). That's actually a common mistake elemental is a type of damage type such as piercing or shadow.
As for your other question, you'll never be able to 'pwn' duster clones With full 2* gear.
I would suggest a blaster in place of the shadow tech alchemer. Although it does slightly less damage, the bullets travel much faster and it suits the play style of a guardian better

Actually, if you're stuck on 2* gear, Guardian will give you the biggest chance of lasting longer in the fight and helping your team. I assume you know that Lockdown isn't about causing the most damage, but about capturing points. That said, the best way to help your team is to use your shield. A lot. Keeping your team's Strikers in that protective bubble will help them murder the other guys a lot, not to mention the HP boost will help you last against solo enemy Dusker Strikers, long enough for you to hurt them badly or at least, get some back-up. Like Xtremejim said though, "pwning" Duskers is near impossible for a 2* knight. Being a 2* Striker is incredibly difficult. Also, it's still no replacement for grinding to get 3* gear. :D

No to my experience, graviton charge is really easily to escape from due to the dash feature all classes get. I would say for your second slot if you want a bomb, you should get Lightning capacitor for keeping caps and supporting your team. If you can't get the bomb then haze bomb would be the way to go [but the trouble is its kromo coins] If its a gun you want super blaster is the most viable choice. Anyway do you have a second sword, because a elemental sword would be nice for pvp and pve reasons. Elemental words i recomend is thebrandish series

For t2 LD i wouldnt recommend using a brandish.

HEYERS I think I saw u a while ago. U has the eye of fury?

If u has access to the t2 OCH u can get the 3* hammer and that will surely give you the upper hand when used correctly.
The sword might be slow but gives an advantage over the forward dash or whAtever it is called.
I currently do not own a hammA (and i never will) because my KAMARIN smash do just fine alongside my swiftie flourish - and yes sometimes my Arc RaZor when i feel abit overpowered :P

~Mountha~