Past developers did nerfs/buffs to classes based on item stats. This was then copy, pasted, scaled, and then changed again. This process has been repeated a few times over the years. There is also incorrect scaling on current gear(t8+) that has been causing issues. This is the main reason for the overhaul.
The revamp removed a lot of content but did not fix the issues stated above. After a time it became more of a issue to find a proper balance to raids so zone wide nerfs to players where added. Then hidden auras were added to bosses to reduce certain classes damage to bosses. This was not a fix at any Blizz or private servers, only a band-aid to the issue itself.
Haste & Spell penetration will be changed along with every other stat. A meeles DPS will no longer be centered around how much haste they have and a casters DPS will no longer be centered around how much spell penetration they have. Making it friendlier for everyone.
Event items will be fixed and balanced to not be better than end-game. This will also open up the option of newer event items that aren’t strictly earned from seasonal events.
Voting will become a new mid-item tier set with stats between raid and donor. Better than raid, lower than donor.