The team consisted of:
Incoming Paragon
Some other Paragon (not incoming)
Interrupt + Apply Poison Ranger
Interrupt Mesmer (me)
2 Monk Heros
1 SF Hero
Koss (W/P eviscerate + WY + stand your ground etc)
I was a Me/Mo and I brought along ressurect incase of mishaps that occurred and we needed a fast res w/o using res sigs. We got up to Shiro + Lich pretty fast without any deaths. We decided not to do the bonus as most of us just wanted to finish and not take any risks. We got to shiro, fought him until he used IO, and then everybody died except for me because I ran back b/c I told them not to clump together but they did anyways along with the heroes.
I was about to leave, but decided to give them another chance and began ressing everybody and I told them to spread out again and run if Shiro attacks them. So we proceeded like this and the heroes kept dying as well as some of the unlucky players myself included. But slowly we picked off shiros health with tons of degen (burning, poison, bleeding) and slowly used guerrilla tactics to take him down, hitting and ressing while he ran away. The heroes were eventually at 60dp while the players were smart enough to run away from shiro by now. So since I was just wanding him anyways (didnt bring any anti-warrior skills >.>) I just told the others to attack while I ressed the heroes as sacrificial lambs while we slowly picked off his health.
Albeit this scenario was very situational, it is still possible to do this mission with a few heroes + real players, and you do not necessarily need a spoil victor/ins parasite necro along with other "required" professions for this mission. As I don't own factions, I didn't have that skill available although I heard it was the most effective in terms of dealing with shiro, but some people like to think outside the box.

I don't know if this was anymore helpful/useful to anyone but it seemed like a good story to tell b/c I was bored. =p