Alright i'll give some info about some classes:
At PvP servers all Mages must use: +4 INT -4 MEN +4 WIT -4 MEN +4 CON -4 STR
-8 stats to Mentallity means -M.Defense and more possibilities get a sleep/root/silence condition,but if we talk about PvP server you can get
Mental Shield Buff, you also like Mage got Passive Skill called Anti Magic that Increases more than other fighter classes own M.Defense.
For Knife users also known as Dagger Type Players at PvP servers must use:+4 DEX -4 STR +1DEX -1 STR +4 CON -4 STR
-9 stats to Strenght means -P.Attack and less attack damage to simple hits,but if we talk about PvP server you can get
Song of Renewal,Song of Champion that decreases re-use delay from all physical skills you MUST use,(simple hits are useless).
If you got a Orc Destroyer - Titan whatever and you wish to make trains with Polearm you must put +CON dyes and you must choose between
-STR and -DEX this is cause you get Max HP and you able to use Frenzy,Zealot skill "easy" without get rip, anyway both skills increase your lost stats strenght and Dexterity.
If you got a "Tank" whatever you must use +CON too dyes to get maximum depend class HP,things change when you want make a Tank against a char into Arena/Coliseum you must use +STR and +DEX dyes,and you must play with Knife(Dagger with Special Ability Critical Damage or Focus).
If you got Healer Class you must use +WIT for sure and you can choose between +DEX or additional +1WIT Dye third slot must be for sure +CON
These above are some usefull dyes by my opinion.
Respect you all.