Good post, put that on the facebook page for the grenades FAQ!
No Facebook account, and I'm not going to make one after succesfully avoiding it for years
Feel free to add it there.
Point of math in addition because of
going 'Krak abuse':
Even the lowliest transport has AV10 in the back. A squad armed with Krak grenades needs a 3+ to hit (Vehicles count as WS1) and then a 4+ added to the Krak's S6, so only using a single of these anti-vehicle
grenades you have a 2 in 3 chance of not doing anything at all.
It gets worse when attacking a Walker, attacking something like a Dreadnought which has equal (or higher) WS that can keep its higher Front armour to you. Your chances with a Guardsman or Space Marine squad of glancing a Dreadnought with a Krak are a mere 1 in 12 (4+ to hit, then 6+ to get the Krak through AV12) and you can't do more than that.
I have NO idea how using every model's Krak grenade in CC would count as abuse. These things are supposed to make infantry dangerous to light vehicles, and that's only ever going to happen by using a large number of the things.
Math on Haywire grenades and Imperial Knights, aka why I suspect this is all their fault:
If allowed to use every model, both Tau Pathfinders and the more expensive Eldar's Swooping Hawks will hit an Imperial Knight on a 4+ (SH Exarch on a 3+, but ignore him), then have a 2/3rd chance to Glance plus a 1/6 chance to Penetrate. Maxed out Squads (10 members) are thus likely to take most of the Hull Points off an Imperial Knight, but need a bit of luck to actually kill it in one round (Especially since Overwatch may cause losses, and the Pathfinders go AFTER the Knight's regular attacks).
With the mobility of both, Pathfinders having Scout and Swooping Hawks being Jump Infantry, this is probably the most cost-effective and reliable way to do a lot of damage to an Imperial Knight quickly.