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Problem is, Inquisitorial Storm Troopers would be the same as their IG counter-parts, same price, same abilities. The thing is, would you go for a 16 point model with a S3 AP3 Hellgun and carapace armour or go with a 20 point model with storm bolter, force weapon and power armour?

well, to add insult to injury we can make a load of plasmagun wielding guardsmen at 14 points, a bunch of crusaders or deathcult assassins at 15 points each with either 2 power weapons or power weapon and stormshield, and a few walking multimeltas at 10 points each... or a real horde of guardsmen with stormbolters at 7 points each - and we can boost them with some monkey business and a lascanon at 35 points... and Lord Coteaz can make them all available in limitless supply!
In fact Coteaz is so broken that I will refuse to play anyone who brings him up. Try fighting 90 multimeltas in 30 squads of 3 each... if the squads were taking slots, this could be mangeable though still awful (72 plasma guns, thanks!)

You havent seen the powergamers around here, their motto is:
Because we can!

termies as troops are overrated, at 40 points per wound...

models themselves are top notch, with all the different nemesis weapons as options!

well, bought the dex...
here are the sky isnt falling after all parts:
nemesis warding staves reduced to 1 per squad, and imho worthy only on independent chars if at all since default sword adds +1 to iron halo inv

servitors do get mindlock if not accompanied by inquisitor - function only on 4+
only 3 plasma guns per henchmen warband

that leaves imho best combination of:
2 jokaero
3 plasma warriors
chimera
2 lascanons/multimeltas/heavy flamers, 3 plasmaguns, plus all the dakka of chimera, together goes to 167 points

by comparison veteran ig squad of 1 lascanon and 3 plasma guns in chimera costs 190 points, does not get jokaero bonuses but has bs4

I can see some mass wyches to death cult assasins conversions coming, ws5 s4 i6 a2, 2 power weapons 5++inv for 15 points, no limit in squad - eat your heart out banshees and incubi!

GK bits of info missed so far
all including termies have frag krak and psykout grenades- last ones make enemy demons and psykers i1

rad grenades, powerful stuff, make entire enemy squad in btb with the bearer -1t, does affect instakill value! fortunately only few characters can have them... grand masters, brother captains, xenos inquisitors and techmarines...
cost 15 points per model, but imho worth it, for the instant death on t6 gribblies (via the hammerhanded demonhammer) and making eldar t2... lol even basic marine without hammerhand does instant death to them then!