As we know we should keep runing skill at low points in a begining, we will not be able run fast around. As the simple reason, in PvP you will be more powerfull having more points in multihit, at level 20, dudes with 10 points in runing will not kill anyone. Why vit is better than dex. 1 dex = 1.6 def, 1 vit = 20 hp. Dex gives more dodge, but you still will get hit eventualy. Fast leveling is all about how hard mobs you can survive. You will spam pills, but you will not die. Dex reduce dmg mobs do to you, but sacrificing vit points for dex is not worth it.

Remember we talk about speed leveling(12sky2 Gold). In slow leveling and no PvP dex can be an option, but this games is all about PvP and vit is so much more than dex in PvP. If you want be tank, you can use this guide for Twelvesky2: you can not kill unless you stun enemy, but its hard to stun because with low str you have low hitrate. You are slow leveler, but you use less pills. The tye you are supported in wars, no domination and sloughter XD. Dex for tank pays off only then you are attacked by loads of enemy like 6 and more.