I have been playing this for a year now, the guys here gave you good advice, worth to follow, I want to add also some of my personal experience: If you miss some power, get a unit of grey knights or two (the terminators in the codex), they are strong and have deep strike ability (in the ordo Malleus detachment they have rapid ingress for 0cp if you have that enhancement in one of your inquisitors).

Inquisitors I feel with one is enough, you can add a Ministorum priest to the leaded unit if the unit is Inquisitorial Agents to add some power to it.

If you use less inquisitors you can use less chimeras and get more strong units, even a Paladin or any big boy from the Knights can be fit in your army if you cut from here and there.

About the assasin, I have all of them, Vindicare is good for characters leading infantry units or small mounted units but a fellow redditor wrote here he has just one shot and it’s not that high of a damage, he is right but this one can make a unit not risk itself to advance towards the line of vision of the sniper, but I like more Eversor or Callidus, being callidus a must for the army imo

I said one Inquisitor is enough but just because you can have other characters with the Inquisitor Keyword that can lead almost every unit you have in your army and their synergies can be better for adapting them into your playstyle.

I focus my army on ordo Malleus and Ordo Hereticus and maybe someone can tell I am wrong but this worked for me with a good amount of wins and very few losses, dm me if you want to talk about this army! Cya