This is my info about using duel combo's.

blade/blade- personally I like this combo because it's easy to level. I got this to lvl 13 in 2 days.in pvp you have a great chance of winning if you can aim your fb well but if you cant u alwayse have herc as your backup but I don't prefer this because u can only herc 3 times and it does low damage.

sword/sword- if you are going to use sword sword I wouldn't get nix until ut at probably lvl 10 with it because your nix makes it a lot slower.If you are going to pvp with this combo its amazing because if u mele u have ur nix which makes ur hits harder and u have ss which will hit high to but as i said before if you can ss you have herc as your backup.

club/club- same as with sword you shouldn't get your rage until your clubs lvl it at least to 10 and lvling your rage takes a few birds it lvls really fast. if you are going to pvp this is ok because if u mele u have rage but you only have herc for a distance attack so its harder to kill people unless ur a higher level.

hammer/hammer- this combo is ok .You can get your skill rite away because this skill only happens every once and a while so your wepon lvl will level fast.in pvp you can only use herc like club club but with this wepon special you can stun ur enemy.

with all other weapons it's the same because you can only use herc and as I said before you can only hit so high at a low level.

if you are going to be leveling you should ovcourse be using a club because of rage.