For me, my Archon have literally did wonders. It excel in what it does, and I really like the fact that it adds that punch I need in my list. It successfully killed enough things by itself to earn its everlasting slot for one of my HQs (the other being its small squad of Wyches into terrain.
A simple agoniser, djiin blade, soul-trap, shadowfield, Haywire grenades and drugs did the job for me as I am armed for almost anything. Not a true headhunter like the HB/ST archon, but it can do so if it wants to using the Djinn Blade. I can get Sliscus of course, but Sliscus proved a little redundant in my list unless I add in even more units to take advantage of his rules.
However I will admit that if the Haemonculi are allowed to take grenades, then I would actually use the points for the Archon to get another squad of wyches or something to boost my list. But alas, they do not get grenades, and thus the Archon will suit just fine. Not that I am complaining about my Archon, but if you really want a more powerful list, sometimes the HQs are redundant.