I think something like this would be neat. Warmode feels odd in general, a PvE reward for a PvP experience. I understand due to this being a PvE server there's some constraints on how it works, but anyone having the first pass on you is meh for 30%.
Something like a PvP reward would suit it better I feel. Maybe rep while leveling for PvP oriented factions. That way there's some incentive for people actually interested in the real PvP aspect while having no friction with PvE design.
I think the 30% xp boost should be moved to a PvE oriented challenge. Maybe mobs hit harder, you have less hit chance, or gear permanently breaks with no repair requiring refreshes, maybe even the OG ironman where you can only use whites and greys. Then it would feel earned and perfectly in line with PvE. There'd still be the feeling that people want to take it because 30% xp esp on this server with custom quests is no joke, but having a severe enough consequence could eliminate the friction of feeling you'd go slower without it since the challenge is making you go slower in general.