There's a huge reason why everyone is saying Sorcerers are overpowered.
They:
A) 1-3 Shot people, with balanced attributes in Colosseum
Outside Colosseum, they can one shot most anyone with a Critical, even without they still do a min of 2-3k damage.
Even A fully geared Wizard can down me when I have no 40% reduction for 10 seconds up even if i stay defensive, all it takes is a stun and it will chew past my regeneration from high heal and rev. All this comes from raw nuking power, because the game is centered around gear stats, most stats are the same.
Unlike Ragnarok 1, where you can have a specifically vit-base priest that can at least tank insane damage but obviously lack offensive. (At least when I use to play RO1 when it was month to month payment)
So in comparison, you have most everyone with PVP gear (excluding cash items and cheats e.g. extra health) come in around 6-7k hp. 7k hp for priests with buff, 6~ for those without, but obviously those with VIP and massive cash items with rune slots will cheat out of it so we won't consider it.
So once again, lets recap, for those that have PVP gear, everyone ends up around 6-7k HP with no cash item and self-buff excluding tanks.
All it comes down to now is how much damage can you dish out, and how much can you negate, e.g. if you can negate the damage taken through heal.
As a consensus its tough to survive a combo from sorcerers, even if you do survive, they can wait, rinse and repeat.
In the amount of time, you'd have to wait through stun before you can react and heal yourself.
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The core reason why they're OP is because stats are all the same, so it comes down to damage.
Sorcerers have the highest damage burst and they have the strongest single quick heal along with regeneration and not have to spec heal.
They can swap between offensive and defensive (while getting healed when spamming defensive heal seal) without any slow-down. e.g. like a priest using sacrament to increase heal by 10%, he/she would have to wait 3-4 seconds due to gimpy animation.
When you cap out around 7-8k hp outside Colosseum, sorcerers can do even more damage than they do in Colosseum due to stat balancing.
They have more crit, more damage, more raw power.
Don't even get me started on those who have +7 or higher weapons, the Crit amount is insane, even without crit, the base damage is at the very least enough to chisel down 30-50% hp.
This is why people consider them OP.
Its like trying to fight a guy with a machine gun using a knife from distance with no cover. e.g. (casting through walls from tab-target) lol.