Well PD is not much more effective than in Dom2, *but* you usually have more money to invest in, so whereas in Dom2 we put either 2 or 11 PD, it's now rather 11 or 21+.
So small raiding armies can be stopped, but as armies are larger also it's more or less the same, unless vs spells that didn't "rescale" such as Calls ..
But, and that's my point
, now stealthy scouts and armies are much more easily detected and defeated.
IMHO that's the real change : I wasn't very fond of stealthy strategies in D2 but now they're even weaker...