I've used MORIS a few times, and can't complain about the service. Although I've never had to claim
Do remember though that their Touristenfahrten cover (in the trackday section, but you select Touristenfahrten/Public Day as the name of the track) is 1st party only (i.e. covers your car only - unless you've taken out the option personal injury insurance).
If you want to reduce the premium, then you can call them and ask for reduced cover to cover just the chassis (as the mechanicals may be fine after an incident), and this will also reduce your excess.
You can also under-insure if you wish, which will also reduce your premium, but of course will limit the payout amount in the case of an accident.
Also check your road insurance policy VERY carefully as it may have a clause which lets them claim back anything they payout that they "would not normally have covered" if not for local legislation. The 3rd party cover under EU law cannot have any disclaimer for not covering the 3rd party, but they can put in a recovery clause to come after you for the fund they've paid out. In other words, if you take out a guy in his Veyron they will pay him, but chase you for the monies afterwards (that includes damage to other cars, and the cost of track closure, barrier repairs, air ambulance, armco replacement, track cleaning, etc.)
I've done a good few laps and never been anywhere near losing it, but that's because I want to drive home in it and will just drive at 8-9/10ths all day long, getting 99% of the fun out of it anyway.