Check out the patch notes for the v20 Lovely Update here: http://maplestory2.nexon.net/en/news/article/55909/lovely-update-v20

So this is a guide for any zerkers (this might be useful for other classes too) who go into chaos raids and see they are missing a ton of damage.
I had this problem for most of my time in maplestory2 (i have been playing for around 7 months now). As i progressed through to lvl 60 i thought i was doing great! BUT the main realisation of how far i had to go came when i did my first chaos raid U_U aannnddd so the real grind began. I recently as of this post began hitting the damage that i am happy with (100mil +) in CDEV and CMOC. I thought i would share with you my tips and advice i found very useful to reach this goal. Of course it is by no means top tier damage but hitting ur first 100mil does give you a really nice feeling and it is nice to know you are heading in the right direction
First my stats:
My weapon is a Legendary +11, with 23% pierce, 5.4% physical pierce, 23% boss damage.
Okay so first the things that may be out of your control:
Internet Speed
Computer Performance
- These are variables that might get in the way and change from player to player, so i will assume that you can run the game decently and have manageable ping. I bring
these two up due to boss mechanics being a big part in the damage output.
On to the juicy stuff:
Pets - Pets are a huge boost in dps!!!!!!! Honestly i didn't realise how much a pet actually gave you since i procrastinated levelling my pet for so damn long. But yes
please please please remember to level your pets. A blue pet will most certainly do if you can't get your hands on an epic! (i have blue pet lvl 35 as of this post).
Gemstones - Gemstones are extremely effective at boosting your damage, more than pet as well. However i added the pet first because it is underrated in my opinion. If
you want a rough guide for which gemstones to put in i recommend 5 of your main stat (strength, intelligence, luck, etc), 3 offensive gems and 1 accuracy gemstone. This
is kinda a meta formation for gemstones, i personally have 4 main/4 offence/1 accuracy, but i am still experimenting so that might change.
Honestly pets and gemstones made the biggest change for me. but lets continue!
Stats and gear:
Head gear, Bottoms, Tops, Boots - For these you want to aim to get Boss Damage bonus on all of these (you want to try to have 4%+ on each if you can).
Gloves - you want to try to get Physical Piercing.
Weapon - Essentially you want some piercing with another good stat like total damage bonus, boss damage, physical piercing, or even strength (as it is your main stat).
As well as this you want to see if you can get a weapon with a higher then average base damage (that is just a bonus, just to juice as much damage as possible ).
Pendants, Earrings, Rings, Belt, Cape - Most of these will have piercing and boss damage on them but other stats like melee damage or physical piercing might be alright
too. I haven't noticed too much difference in damage with attack speed stat but i guess over time it might be useful? For cape i recommend Balrog Wings as they have
ideal stats of a zerker.
Hmmmmm yeah those are the most important things to get ur damage up to scratch!
My build is just a ground slam build with blood price. For damage while recovering i use the first ability, since it takes no spirit to use. Honestly build won't make a difference until you have the above stuff in check. I tried so many different builds during my time testing and sure. the damage changed but in the end i was still doing like 30mil max in dungeon lol. I do recommend the usual ground slam build tho. You can experiment with adding groundbreaker and stuff with it later on too.
Last piece of advice is to not die xD, try to stay on the boss as much as you can and really get used to the mechanics!
Hope this helps just felt like i should share my personal findings after struggling for so long with damage. Still a long road ahead but it is nice to know i am moving forward.
Good Luck!