Rely on well-known, established community forums rather than random sites.
Known for being one of the most stable and heavily populated Legion servers, with a focus on blizzlike mechanics.
The primary reason for the deep dive you're about to undertake is simple: Blizzard no longer directly supports or offers the 7.3.5 client for download. Today's official World of Warcraft client is a completely different build, having moved on to newer expansions like Battle for Azeroth, Shadowlands, Dragonflight, and The War Within. If you install the game through Blizzard's Battle.net launcher, you will get the modern version of World of Warcraft. While this version includes all expansion content through a subscription, you cannot "downgrade" it to the specific Legion 7.3.5 state. It's a one-way street to the current live game. The Legion expansion, as it existed in 2017, is essentially preserved in time.
The Mythic+ dungeon system saw massive quality-of-life upgrades, better reward scaling, and refined affix combinations.
Use a torrent client to download, which allows for pausing and resuming.