Blowpipe, don't forget the blowpipe. I dunno if it works against high-tier enemies, but against early game ones it is superb - looks like a 100% chance to put them into sleep. And they stay drowsy until you hit them (in the back, obviously).
You can still do tanking lizardman barb. He's not as good as the insectoid, but he's obviously superb against anything magical.
What are the stats of the endgame heavy weapons, btw? And heavy armors. Just curious, with all this restarting I can't get past the mid-game, lol.
As for the insectoid knight - I thought about that, but he's very, very slow to build up. His protection bonus starts crappy (when compared to the battlemage that, if he finds a certain secret, has that +10 prot enabled from lvl 2), and he need 2 points of armor, 3 points of light weapons (so he can use backbiter's special - self-healing tank is a good tank) and 5 points of dodge to start doing something (which is a freaking lot, all in all). Another problem is that his dual wielding really conflicts with his desire to wield shield(especially once they fix his knightly bonus). All in all, he's just inferior to the battlemages - he's not that much better of a tank, but his damage output is much lower. And that's the problem of all kinds of knight, tbh. I guess they're ok if you have alchemist in your party and need someone to throw the bombs (and the alchemist himself has better ways of dishing out damage), but that's pretty much it.
Or maybe you go for something like a maxed out STR&Dex lizardman knight and, despite getting dex buffs & evasive items, still invest into heavy. Probably progression is armor&heavy->armor->max out heavy->max out dodge at lvl 11->max out armour.