[Squirrelloid]

I wouldn't counter Shishi with thugs. At MR 16 I'd blast them with mindhunts (they'd die pretty easily to pen+5 mindhunts, even with an AMA). And I'd use battlefield magic to kill them.

MR 16 is pretty weak sauce for a thug, so as long as you can make penetration boosters, I'd be tossing the following at them: Soul Slay, Enslave Mind, Charm, Control, Disintegrate, Blindness, Paralyze.

Not MR dependent:
You can tie them down with prison of fire, tangle vines, vine arrow, earth meld. You can sleep cloud them or use rigor mortis to make them rack up fatigue. You can blast them with evocations (banefire, magma eruption, gift of the heavens). You can cut their effectiveness in half with darkness. You can Drain Life them. I could probably go on - that's just off the top of my head.