Talking about PVE, until which extend?
This is due to Rank 8 PvE is a HUGE spike compare to Rank 7 and below.
And the ultimate PvE content is Earth Tower, which require a very committed/hardcore party or guild and investing of at least 500m silvers to be a DPS player there.
Why Rank8 (lv275+) is a huge spike? Because all monsters have hp like 500k hp, some archers/mages have 1 hit KO abiity which u need stack a lot of pdef/mdef, and some mages have 2.5k+mdef which your magic only deal 1 damage and you need stack up to 3k matk to barely kill them.
Some R8 monsters have link-resist will have headache time but the quest still barely do-able.
Considering the viable build, low cost and easy mode for beginner:
Wizard C1 > Pyro C2 > Linker C2 > Thaumaturge C2 > Sage C1
Wizard C1 > Pyro C3 > Linker C2 > Thaumaturge C2
Wizard C1 > Pyro C3 > Linker C3 > Sage C1
For normal mode:
Wizard C3 > Elementalist C3 > Warlock C2
Wizard C3 > Linker C2 > Runecaster > Featherfoot C2
Wizard C3 > Linker C3 > Warlock C2
Why psychokino and sorcerer is not so viable in Rank8?
Psychokino, unlike Pyro have Agny Necklace, the damage is so low and slow that hardly kill any R8 mobs. Same to Sorcerer summon