LOL,well, I played sinx for the first half of my years here, and i was never a breaker as a sinx. I was a PvP sinx, and I practically hit everyone in anthell01(that was the pvp hang out place when i played sinx). That taught me tons of things, including the weaknesses of melee classes. I never tried sniper and champ, but those two gave me a hard time as a sinx, so when i went to biochemist, I made sure that every class there is, i have some sort of defense. No need to get super offensive, you need something to be able to fight every class, even if you can't beat them.
You guys need to pvp, don't care what others say about randoming being annoying. annoy them. Kill everyone, not just the ungeared if you are just starting. That way you will know what is the weakness of your class, and put some kind of fix for it (cards and skills).
I'll give another example. RSX armor screws bios, so i have one acc that has strip armor. knowing pvp room dispells fcp, i know that if i cant break their armor, they are using rsx(add the fact that if my storm gust dont push them around). in fact, i normally cart revo them first, if they dont get pushed back, i switch to strip armor and strip away their armor and weapon using metalling card too. and once they get frozen by SG , i know they dont have armor. i use this strategy against SN too, i know for a fact that they have low vit and 500k hp with two tao, even if i spam i cant kill that, so ill remove the armor then spam.
There are tons of things i can't say outright since i will be giving all the stuff i use. but frankly they are not secret combo cards, most of the stuff I use are pretty basic. (HINT: some of it are custom cards :p).