Found this through the Guide to Guides, and I must say it's enlightening.
On my lvl 43 fire/emp imp herder, I've got assault and tactics; tactics 1 end red, 5 tohit+
I've slotted my monkeys 4 recharge, 2 damage ever since I got them, which was after the big patch. I enjoyed the fact that they got way more hit points and accuracy, so I wanted as many out as possible. 6 recharge is a bit much; with 4x2 all greened up I get a full 3 sets out, which is as much as 15 flaming monkeys!

With a teammate with speed boost or AM, I can get 4 1/3 out, pretty much. I've actually gotten 2 speed boosts and an AM on me, and let me say it was nice
The only problems I have with that many out? I'll get stuck inside a little room in the office mission maps, or similar confined spaces; also, my melee-only teammates have trouble competing sometimes. Frankly that doesn't bother tankers nearly as much as scrappers: tankers can at least taunt/provoke and do their job, even when they can't do the punch-voke thing. I play in large enough teams, though, that there are plenty of mobs to go around. The monkeys make it all go faster, so I get to pay people back for some of the sponging I had to do to get to 32.
If I had to redo my secondary, I'd definitely pick radiation! Kinetics is also a good secondary because of the nature of the heals, but you can't speed boost yourself. The good thing about an empathy secondary is I could advertise myself as a healer to help me get to 32.

I would think fire/storm would be toughest; at least with FF you can bubble your imps, and the force bubble type powers may be useful...
I'm going to try getting rid of leadership in favor of stealth and Phase Shift; if I do, I'll try it on the test server first, and I'll also test the 3x3 slotting on the imps to see if that works well.
My opinion is generally, more imps=faster kills, regardless of actual damage by the particular imps. Kinetics and Rad secondaries shouldn't even bother with leadership or damage slots on the imps, and go with more recharge, and maybe an accuracy. I personally wouldn't waste an end reduction in my monkeys, but at this point I have both RAs and conserve power