All campaigns suggestion: Introduce rare spawning mini-bosses that drop rare vanities

[Physiologic]

Forgive me for the length of this suggestion, but as in all things I feel strongly about, I will write in excess.

Background: A month or two after the Shadow Caves were released, player interest in farming this campaign dropped significantly due to the high level of difficulty. The Shadow Caves is now extremely empty and void of any sort of activity whatsoever. I believe it was Cinco who designed a rare-spawning mini-boss that would drop the legendary Vyxnaar Helm of Hate in an attempt to improve replayability. Interest sparked once more for this campaign, but again the difficulty of this elite dungeon outweighed the benefits. The concept and implementation of rare-spawning miniboss was abandoned in Nuri's Hallows and Mt. Fang.

Current issues:
1. Replayability of old campaigns is a large issue when a new cap campaign is released; this is obviously common sense as most players will flock to new content. Once most players reach cap level (or elite cap level), most likely they will never set foot in previous campaigns ever again, as these campaigns do not have much to offer them.
2. Rare vanity and pink drops are a bit too rare in current cap-level campaigns as evidenced by player complaints on running dungeons constantly 1xx-2xx times without getting a single pink drop.

Solution:
Introduce rare-spawning mini-bosses in certain maps in old campaigns and new campaigns. Specifically, Alien Oasis, Balefort Sewers, Nuri's Hallows, and Mt. Fang. The appearance of these mini-bosses are obviously up to you, the devs, discretion but having them spawn extremely infrequently (1 in 100 runs) may also prove to be a deterrent to run old campaigns. These mini-bosses can drop specific vanities that are specific to each campaign that, when combined together, will form set bonuses. For example, Mt Fang has the rare dragon vanity set that only drops in that campaign, while Balefort Sewers can have a rare super unicorn vanity set that only drops there. Mini-bosses that drop rare vanities also improves a player's odds of grabbing a vanity without directly affecting a main boss' odds of drop.

I believe replayability in old campaigns will improve once players reach cap level, as they do not have much else to do except keep running the same maps over and over again until they get more end-game gear to sell.

Issues to think about:
1. Minibosses difficulty - should they be extremely strong or should they reflect the difficulty of main bosses of the respective campaign?
2. High-leveled players entering zones where lower-leveled players are in may cause some problems such as kill-stealing or begging to get power-leveled.
3. Vanity stats/appearance - how strong do the vanity stat bonuses need to be, and how awesome do they need to look to provide more incentive for players to farm older campaigns?

Thank you for hearing me out.