I bought my expansion pass three days after buying the game. The game came with a slip in the case advertising the expansion pass. If you read that "official" piece of advertising, you will see the word raid doesn't appear on it!
They never promised people a raid with each DLC. They promised strikes, missions, PVP and PVE content. Gear and weapons.
They added a new raid with Crota and they failed miserably and rather than make the same mistake again they're taking their time.
Just accept what they're giving you and stop complaining about every detail. You've properly played over 400 hours at this point, probably more. For £75 id say that's good value for money.
If the games that bad then trade it in!
Agreed, Crota wasn't a failure by any stretch. It's fun to run with a group......well when you can get one together. It may not have been as challenging as VoG but it was far from a failure IMO