Despite the Issues with lag and grindy nature of the Fortress Seiges when it was first introduced, it did have some good potential.

I think with a few tweaks it could still be a majorly fun part of this xpac.

I'd start by adding some good reasons to come and actually complete the event.

1. Make each of the 5 mini bosses and the final boss count towards "Zone event Colossus" for purposes of upgrading gear.

2. When the event concludes let's have it award 250 or so Intel.

3. During the invasion phase the enemies didn't award planarite. With the huge need for planarite now let's make ot so this event is a viable way to farm planarite.

4. Let's add new harder Queens Focus boss for completing the event with new rewards. Separate from the existing one.

Up the HP on Hexethel by around 50% and have it hit about as hard as a T1 boss. Boss would have a chance to drop Tenebrian Engines and a hefty sum of Fortress Fragments. 40 would be about right in my opinion.

5. Add some vendor planar essences that can be purchased with somewhere in the range of a hundred or so fragments. These would be slightly lower in quality to the Raid Rift essences, but you could see what you're getting to fill in the gaps of what you need. Also make them unique so you can't just stack one type.

6. This is also an opportunity to add an eternal weapon substitute as a reward for alts/new players.

For say 250 fragments add a weapon for each class that starts as LFR quality and upgrades to a weaker T1 without the eternal procs.