Many say that this mission is the hardest one in Nightfall campaign and almost impossible to finish it solo with h/h. There is great guide on Wiki but they didn't help much about Shiro, toughest enemy that is super hard to defeat. I will describe only how to defeat Shiro so please use Wiki for the rest.
When you close all 5 portals and gate to the shrine is open do the following:
1. Set up green flag for all your h/h in front of the door so that their action range is just short of the door.
2. Use your own character and enter slowly to draw attention to Shiro.
3. Wait until he comes close and then run for the door.
4. Shiro is preprogrammed to run up to the door and then he returns automatically. Whole idea is to exploit this.
5. Attack Shiro outside the door and wait for your tank to come and fight him. In my case it is Koss.
6. Run away further from the door and start ranged attacks and spell.
7. Koss will soon die but healers should do the job and resurrect him. As soon as Shiro starts running back follow him and attack him then run again where your tank will engage him again.
8. Be sure that healers, spell casters, rangers never come close to Shiro or your tank because of Impossible Odds, deadly skill used by Shiro that can wipe out your entire party. If healers are OK then resurrection is no problem.
9. Be extra patient, it will take 15-20 minutes to defeat Shiro. The most important thing here is where you set your flag, not too close and not too far from the door.
After defeating Shiro, use same tactics to lure Lich. He is much easier to dispose. Be sure to have spell breaker skills. When Lich dies mission is finished. Bonus shrines are worthless and you risk too much. with this strategy you can defeat Shiro 100% every single time.
This is not a cheat but smart play. True cheat is Impossible Odds made by programmers to make your life hell.
This is exactly the same strategy as for final queen boss in legendary Unreal game.
R

there are no necro henchmen and there is only one necro hero which I didn't take.
There are three necro heroes in Guild wars