The Ld7 bs3 pinikes greatly benefit from the "+3 to psy test" rule. With a plain
ld 7 to cast their one and only attack they would be near useless.
Besides, lots of rules in the dex is written to benefit you in fighting another Daemon army (fluffwise, this is great I think!), and there are some tricks there to lower your
Ld, (doomstone, for example).
But no
LD test on more than 10; you would need a specific rule to modify one diceroll with +3 to get around that.
Edit: no wait, the rule actually work as if you modify one dice roll with -3