So lets cover your post Your saying Sins are hitting 600-700 Damage Which I doubt as I'm a level31 Sin in best gear for my level and only hit 250-400 with Lotus with all buffs so unless red poison is being used and at that point it's not sins being op it's sins utilising a Taoists best group mechanic.
And you have an Issue with the sins... People like you make me mad your throwing around the word OP because a few sins who have played pretty much 24/7 since launch are a higher level than you but don't say anything about how fast Wizards are catching up now isn't that funny I'd guess your playing a wizard like usual...
Loads of testing was done Pre-Launch and each class got balanced for certain roles of Which
Wizards are Group damage Dealing Kings So long as their aren't too many ranged monsters they can kill and level faster than everyone.
Assassin's are Single Target Damage Dealers Can kill subs and harder monsters earlier than other classes but cannot facetank Subs Until BF or kill more than 1 WD monster at a time without risking death.
Warriors are the Tanks who excel is survival due to potion mastery and Defiance and can Facetank 2-4 monsters in WD quite easily giving the Sins time to reduce the groups.
Taoists are Utility Specialist they bring Buffs, Heals, Poison, and Super Tanky Pets and If your a good Tao you put your pet in the clippers line of sight during clearing other monsters to save everyone else pots.
Yes Warriors and Taoists have it a bit slower levelling than Assassins and Wizards but Once Taoists get Shin their beasts and Once Warriors get Destructive Surge They can do JP/BP without any issues where as the Assassins will struggle in places like JP/BP forever due to low AC, MR and ranged monsters that's ignoring the Para in their which is Aids for the Assassins.
As for PVP that was Also tested and for the most part the classes were balanced, and IMO I think Warriors once they got shields were Tanky as hell and Taoists were annoying as hell running around their pets. So personally I don't see an Issue if someone who is playing more than you is out levelling you.
So Either Multi like them, play more, or group up and go WD instead of crying about class balance when it's perfectly fine in the grand scale of things.
Also one last thing I remember official Before Assassins and After and the Way Warriors Always worked was they Out geared an Area then went their to level they never really Solo'ed WD, Snow as it was too much work Instead they went to places like JP/BP hit the MR cap put on elemental stone and laid waste to large groups of foes which let them keep up with levelling against other classes and get some of the best drops in the game baring boss drops. 38 Weapons, Rings, and Armours Which if you look at everyone's gear are not in game yet so think of all the money the Warriors will be raking in once they get to late 30s early 40s will be a lot more than a Sin is making hunting lesser subs a few levels before you can.