Another question to add into my mix here would be regarding higher tier MPVs like Orc Hero and Mistress -- I'm guessing those are only soloable in the 150 range with the higher ones being group-only?
Keep in mind that the brunt of my RO experience is from the open beta, where a thief with at least 200 red potions could kill Bapho, so suddenly seeing all these simple enemies become weapons of mass destruction is somewhat jarring.
I had a technically-failed battle against Phreeoni, in which I was able to do enough damage and survive long enough to win, but due to spamming Counter Slash and Cross Impact I kept having to stop to regen SP, so I assume if I was spamming blue pots and not giving him time to heal, I would have been successful, so at least I don't feel like my somewhat strange sword and shield build is completely ineffective.
Melee + EDP is a GXs friend with the occasional rolling cutter to clear the mobs out once in a while.
I can never understand how melee classes can pull it off, unless a lot of the 3rd job skills scale to level or something. I mean, level 5 Counter Slash is averaging like 5-6k for me, maybe 7-8 with EDP (I think!) and I can't seem to get it higher. I've had better luck as a burst damage cannon by firing off Soul Destroyer while standing in strings, but even then it's still 5-6k, just somewhat rapidly and safe from the MVP itself for the most part. I've tried a few combinations of weapons and icepicks and all that and I can't seem to get anywhere near the 20k+ hits that seem to be needed to have any chance of beating an MVP with over a million HP in any reasonable timeframe.
Again melee / rolling cutter with EDP is your friend. The proc from a +9 KVM that gives you max ASPD helps a lot as well. I've killed MVPs with 1M plus HP ( whatever that ugly newest one is on that volcano) my baby ranger that does 7K / second so a GX getting waht at least 3-4 swings per second should be able to out DPS me there.
Also in response about the glorious katar, unless I'm reading about this wrong, I still can't comprehend how that could pull off 8k hits, since the double attacks can't crit, I can barely pull off 1k double attacks with my elemental sword, unless I'm expected to have this katar at +20 on top of everything else -- I don't see where that kind of damage output could come from.
The katar has a relatively highish ATK as well as bonuses against demihuman. At +9 or higher it has a chance to activate max ASPD for a few seconds. Crits are also calculated BEFORE double-ATK. Basically the calcs go crit > DA > normal attack each swing and stop at a successful roll. Example swing one you miss your crit roll but hit your DA roll, DA goes off and you go to swing two. Swing two you hit your crit roll and go to swing three.
That said, like everyone says, gear for the MVP you want to fight. Orc Hero is pretty easy nowadays actually, I can kill it on my genetic with cart cannon ( 12-14K damage every 2-2.5 seconds or sosince I have no god items and use a shield so don't use the big axe ) with no pots at all if I am fully demi reduc wearing and have 3 base AGI, if a GX can't out DPS me with their fast as hell ASPD + EDP + crits on a single target there is something wrong. I mean even my ( at the time ) 108
baby ranger could solo hero with a handful of fat NPC white pots. Orc LORD on the other hand is a bit more of a pain in the butt because of his Earth Quake hurting a bit plus his archers tend to spread out a bit. Phree you just melee to death, it doesn't really do all that much other than stone curse spam, same with pharaoh... although with him it's not SC it's coma / dark blessing ( takes you to 1 HP instantly ).
TL;DR version: gear up for what you want to fight, both DEF wise ( armor mostly ) and offensive wise ( good weapon + EDP ) and get to know the MVP you want to fights skills. And party a bit for MVPs, a FS class really cuts down on your pot usage somehow.... especially at lower levels, once you reach mid 120's you should be able to solo quite a few MVPs with easy.