Angels are not crappy, they just are not very effective against a wide range of people. I would use them against cloud giants at the low ranks but at the high ranks... unless that cloud is a druid/healer or has really piss poor defenses (non village axe spec for instance) you just are not gonna get a lot of mileage out of them. Duergar is fine cause they can be wrathed/holy word etc. Even if they hit hard if they don't land hits they are not doing much, which is why against people who defend well you are better off using a servitor who will deal more direct damage (angel vs evils, challegha demon, sometimes morosa demon, devils) because the direct damage by passes the characters inherent goodness at defenses. Very few characters are both strong defensively and have a lot of dam redux.
Even if they have recite you have dispel magic and given your wide range of choices as a conjie you should prolly be using it in almost every single pk fight against any opponent as most people use at least one low level prep you can knock off.
Bypassing physical resist doesn't matter if they are not hitting them.
The thing is if you are fighting demons are not likely to turn on you anyways. They only get mad when you are not fighting. As a neutral demons will turn on you less then angels by the way if you have not had that experience. Demons are also easier to conjure then angels because you can put in less mana and get more out of them, no 1000 mana winged angels.
Conjies really don't need any cabal powers and being fort is a huge penalty to playing a conjie. So much of being succesful with a conjie is timing things and if you have a smaller enemy base then you have fewer times you can take advantage of the fact that you got everything in high gear.
Harder/easier all depends. I can tell you that yes it is easier to gear off of mobs with a goodie conjie (goodie acolyte being the best as you can altruism your elemental for those tough area attack mobs). But it is really so much easier to use your tools as a conjie to jump a well geared PC at a time of weakness and just take their armor, I mean that might take you a time investment of 1 hour vs 6+ hours going after each of those super tough mobs. Gaunt, tesserect, familiars, clairvoyance, clairaudience, projection, phase door, all are excellent tools to basically set up assassinations on well geared people, it also helps that in general conjies stack up waaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaay better vs mage types then melee types and you tend to want mage type gear.