Hello.
I love invasions - really I do - at first they were great. You've felt threat of the Burning Legion that was invading Azeroth, but in the end... They're invading only 6 zones. Even if they boost invasion frequency and number of simultaneous invasions, there are going to be 6 zones, that no one cares about, under Legion attack. After people get their achievements and gear, they will just stay in the capital. Why doesn't Legion invade Durotar or Elwynn? Stormwind or Orgrimmar?
Main capitals would be under constant attack, with Warchief / King rallying their forces and fighting. If someone would say "I can't do my auctions" or something like this - there are other capitals than Org or Stormwind, such as Ironforge, Darnassus, Undercity.
More frequent invasions are good but they don't add immersion. The world isn't burning, it's only 6 areas.
Don't take me for a whiner, Legion Invasion is one of the best pre-expansion event and with this potential, Blizzard could've done much better.