When is a Night Lord considered fit for bossing

If you don't have base int, 13x is totally fine for zakum, krexel.

 

It depends a lot of your squad, your base int, your gears.
If you got good gears, you can still do bosses with int without having much trouble. Remember zak/krex are lv140 bosses, so you will have 1% dpm loss per level below 140. You should be good in 6 man parties with SE tho.
I would look for a 71 craven, 12 att gloves and 3 or 4 att cape with luk/dex scrolls to start. Grt some ilbis too. Shouldnt be hard to get those gears if you farm at nightghosts. Or if you have mages, it's even easier. Those gears will be enough to carry your own weight at mid game bosses.

 

Have you considered remaking? As an old player, you might have some high NX account sitting around. Leveling isn’t quite as hard as it was back then nor is gear progression. Some extra HP (even accounting for challenges system) will always help as HB is no longer a necessity to survive.

Other than that on the dpm front, your NL is playable bc of your lack of int. If you want to play really casually, some upgrades (like the ones suggested above) and higher wa pots (makes up for gear differential) might help.

 

You should be okay to wash out all of your INT now because your current washing efforts will be overtaken by the challenge system entirely.

 

The challenge system allows players under certain HP thresholds to gain more HP. It doesn't matter if they washed or not, as long as they're under the promised HP threshold, they should be eligible to gain the HP to match whatever the system gives. So, if you are lvl140 and you have 6k HP, the system would give you 800 more HP to match the 6.8k it promised. If you're say 6.2k HP at 140, you will only get 600 HP to match the 6.8k HP. But if you are above that then you won't get anything.

 

To be fair, nobody really cares how high your damage is for zak/pap/rav/krex! Don't worry too much~