General

You don't need 200? are you sure?

@chaosh you max the zero link once you complete the story that mean 181

I have no idea how much range a Kanna actually needs nor how to solo C. Vellum, but I know enough about the game mechanics so that I can try to help.

The ~20m hits are definitely minimum damage non crits while the ~40m hits are max damage crit hits. The inconsistency isn't really a problem since most of your hits are criticals anyways, and I'm guessing your average damage should be around ~37.6m, so according to siapmystick it is enough damage. Although it would be nice to make it more consistent, which means increasing your crit rate.

Assuming I understood correctly, with 68 both min/max crit multiplier and 87% crit rate, getting to 100% crit would increase your average DPS by ~5,55% percent, which at this point in the game is quite a lot (and worth the effort). The problem here is that leveling Phantom's link skill will give you 5%, BT's is 3% and a level 200 Marksman character card is 4%... So you will end up with 99% crit. Damage wise that 1% is fairly meanless (0.4% - Yes, I love doing maple-related math), just annoying.

One of the biggest damage increase, however, will come from defense ignore. C. Vellum has 300% PDR/MDR, which is pretty ridiculous, but also makes every single point of defense ignore extremely valuable (although it stacks multiplicatively, so it's also a pain to get), getting to 91% def. ignore will increase your damage by 4.28% (8.57% if you manage to get it to 92%), so it would also be recomended to level your Luminous (link skill), Zero (link skill), Beast Tamer (character card) and 3 pirate classes/Xenon (character card set).

Now, leveling so many characters to level 210 (BT, Luminous, Phantom and I guess Zero? I have no idea how Zero link skill work) and 200 (Marksman and at least preferably Shade, Mechanic and Xenon, although any 3 pirates will do) is very time consuming, but in the end you it will increase you damage to ~42m average damage per line (so around 40~44m lines) and you won't actually have to spend hundreds in NX trying to recube already godly equipment. Or at least I assume all this effort is enough to actually kill C. Vellum as a Kanna, don't forget to use Mana Balance to keep your mana as high as possible (the fact Vanquisher Charm costs more than you can regenerate after the revamp annoys me so much...).

Should I go for level 3 links for phantom and bt then? I eventually don't want to use this crit ring cause I'm missing out on stats from a better one. As for inner, the luck I get is bad otherwise crit wouldn't be such an issue

@msnite: for all endgame bossing u ideally want 100% crit. Try to get this from link skills and character cAdd and inner, last resort get it on a bpot or pot

With dse my min and max rate goes from 49 to 68 (crit ring) with 87% crit rate, normally 49-53 77% Also 90% pdr when buffed and normally 208% boss but if i can get that bellflower off 253%. Are these stats enough?

Hi,
The following advice is based on the somewhat lacking context you provided, and my unfamiliarity with your understandings and with your Kanna character:
-It might be optimal to cast Mana Balance as frequently and opportunely as Vellum's head is underground.
-The inconsistency in your damage lines might be attributed to low critical rate (if the 20m lines are not critical), minimum critical damage, and/or untimely absence of Haku's Blessing.
-You might want to reduce more monster defense (recommendation of at least 90% when buffed so that Chaos Vellum ignores no more than 30% of your damage output to normal element-resistant bosses).
-Higher critical rate and more minimum critical damage should help stabilize overall damage output.
-If much of your abnormal status resistance is reliant on Foxfires, you should still try to frequently dodge Vellum's stunning rocks.
-Note or remember that Vellum's tails do not receive any actual damage.
Consistently inflicting around 35m Vanquisher's Charm damage lines should suffice for the purpose, provided the personally fitting dexterity and coordination.
Hope you're making good progress!

The only tip I can provide, as I do not know a lot about Kannas besides Kishin, is get as much Pdr as you can! Good luck