I do not have a DK, but from what I understand Berserk gives you a considerable damage increase when you are below 40% hp I think it is... correct me if i'm wrong. If you hp wash (which is very easy for warriors, and even easier for DKs due to always having access to hyper body) the amount of hp you'll have while in the required hp range for Berserk would need to be above the necessary amount for whatever you may be fighting. For example, if you are at HT and you never washed and had 15k hp after HB and wanted to use berserk, you would need to be below 6k hp. I'm also not super active in HT being an i/l mage because no one wants me there... but i'm pretty sure 6k is roughly the minimum so you'd be on the edge of death most of the time. HP washing is not a MUST, but its very helpful and I would strongly recommend it. Like I said, i've not had a DK, so maybe you'd like a second opinion.
Just wash its not that bad as dk gets 50-54 hp for only 4 mp and you got hb So just wash ao that your hp×0.4 = monsters hit (will be changed to hp×0.5 after source)
If you plan on staying on the server for a while and becoming 160+ (which is much easier then it seems) you'll probably regret not washing. For a DK its extremely cheap and easy to hp wash. Thats just my opinion though, you can do whatever you want. I've just ran into way to many people with the same mind set as you have and they end up having to make new characters.
I suggest you read a guide first, such as: http://www.royals.ms/forum/threads/fully-revised-hp-washing-guide.8286/ If you have any specific questions after that, feel free to ask Edit: Some additional info. A warrior will need about 400 washes to reach max HP, which means you'll need about 1600 excess mana to wash out.
