As far as I'm aware, the issue of the death penalty isn't that it costs 6k to loose only 5% of your total XP, its that, post 15, that XP is significantly harder to get - thus its a matter of time, in real life, being gobbled up for a mechanical reason.
This is why people find it frustrating, or why people lash out - or otherwise get discouraged to play. It also doesn't enhance the roleplay aspect of the sever.
People treat, IG, death as a minor annoyance, the current death penalty doesn't change that - making it worse won't change that, and making it easier won't change that. When it comes to Roleplay it needs to be instead on the onus of people playing to show the results of coming from near death. Or - change it so no one actually "dies" unless they're perma'd, and instead are considered to be at the brink of death, or downed, or whatever terminology you use.
Death isn't scary right now because you can get back up, its just annoying, from a purely OOC perspective, that a player's time was wasted.
right now, a level 15 character will, at the minimum, loose 5,250 XP upon death, and a resurrection.
that means a character needs to amass 110,250 XP to be safe at level 15? Except, not, because 5,513 XP is now lost on death, so you really need closer to 5,700 to be "safe" from loosing you level, in the best of circumstances. This is actually 38% of the character's current XP towards their level.
Now you get 5,700 XP to be safe, either from ticks, or DM events. if the average tick is roughly 15, per 30 minutes or so, that's 190 hours of time to amass that amount from XP ticks alone. I don't know the actual time for each tick, I'm currently estimating.
Level 16, your minimum XP to not loose a level is approximately 6,500 XP, or 40% of your total XP towards your next level. Once again now your ability to get this "buffer" is reliant on ticks, or DM events, or two quests, if I recall right, that give XP for these characters. I'd ask what is the average XP a DM event will give - to the people that survived. If its 3k, you need to survive two events to be 'safe',
I'm suggesting that someone can't loose a level - you do that, and progress can be lost, but nothing that causes you're character to actually regress in their abilities as a person. lets say like, 30% of the XP needed to make it to your next level, not reducing your XP to the threshold that delevels you, as an example. then 20% for Raise, and 10% for resurrect.
If we're going to talk numbers, lets look at the numbers that effect the character directly when it comes to death, which is XP, and by extension, time.