Yeah. Honestly, they should have gotten rid of the d% system all together. I know, heresy, SACRILIGE!
But it's the best thing for the system they could have done I think. Linear dice systems are kind of flawed, and percentile especially. Should start using a 3d10 system or something akin to deadlands instead imo. 'Sides, its not warhammer unless you're throwing buckets of dice
As for the dh1 psyker system, its 10% per dice, but you don't have 50% chance to trigger with 5 dice. I much prefer it to the current system partly because it is a unique dice roll, which helps enforce the fact that psykerisms are different, and also because its a much more variable scale instead of a binary switch. At least DH2 doesn't have fettering so you can never avoid psyphen. I really don't like merging psychich phenomena and perils either.
See, I always found that pskyers are completely overpowered and ridiculous. They're like any regular acolyte, except they can also turn invisible, guarantee their next attack will hit, float, regenerate, and use what is probably the best melee weapons. But they were always balanced by the fact that each time they used their powers there was a slight chance that they would die, irrevocably and unpreventably. Or even worse, create a tpk. The higher powers really balanced this well, to make them likely to trigger, you had to roll lots of dice, but rolling lots of dice is dangerous, so you want to roll less, but then you might fail to manifest and waste your turn.... The results in general are a lot less dangerous now I feel.
I liked my psykers as walking time bombs with lazor eyes. It also gave players a good reason to actually dislike and distrust psykerisms like the fluff says one should.
Technically they should be d6's if you want to stick to Warhammer! (Actually, I might have supported porting over to a d6 based system since that would have made it cross compatible with the 40k TT! But that's neither here nor there.)
I agree that the Psykers were more unique in DH1 but I think the WP based system is much cleaner. If you want to remove the "no peril" nature of fettered use than simply house rule that ANY manifestation role of Psychic powers role of 95-100 triggers a Psychic phenomena roll regardless of Psychic strength used.