I is shocked.

Are LSDs common in other Jags?

Does it need it?

You found this out by not leaving 2 black stripes? Or by jacking rear end, rotating one wheel and observing other wheel rotate in opposite direction? When for a LSD they should both go the same way.

Older ones, not sure how common or if option. Suspect more likely on XJS and more sporting versions of saloons. Some had a preloaded clutch pack and no ramps so didn't lock tighter with more slip. Once worn the torque transmitted between shafts was reduced. The type with ramps was kinda self adjusting, as plates wore, the clutch pressure plate rode higher on ramp maintaining locking torque.

E-diff Wheel with lack of traction has brake applied producing a torque. An equal torque will drive the wheel with grip. Max drive power when active is half engine power - must calm things down quite a bit. Not sure if it can be switched off.

It comes with traction control as well.

The new XFR looks like an awesome piece of kit, it's got a fancy rear diff with plenty of electronics going on, but then it does have 508bhp from a supercharged 5.0 V8. I can't remember the stats off the top of my head, but in gear or anywhere really it lunched an M5 in straight line and when compared with an RS6, the new 572bhp twin turbo one, 50-70 in 1.9 seconds for the XFR, the RS6 takes 2.8 seconds...

The top model (so far) of the new Alfa Mito has Alfa's Q2 E-diff, but you can't turn the, and I haven't made any of these up, VDC/ASR/CBC/DST off so you can't actually get any real benefit from it apparantly. It's only got

Nope, but the driver does...