So on the never ending quest for trying to find a niche or at-least something good to say about about every unit in 40k has led me to the genestealer. I love these guys. They were the 1st 40k models that I bought and painted. So why has the genestealer been told to get to the back of the nid bus in 6th edition? Lets look at the pros and cons for these guys in 6th:
Cons:
1. Probably the biggest kick to the nards is the inability to assault after an outflank or infiltrate.
2. They don't shoot. 6th edition is about shooting.
3. Point cost (14) for a 2 dimensional unit. They move and assault, leaving out an entire phase of the game. 14 points is too much to not at least have a crappy shooting phase. Not to mention additional stuff like poison and adrenal glands is extra.
4. Brood lord can totally fail as a psyker
5. Bad against 14 armor
Pros:
1. A horde of them will kill almost any dedicated assault unit in the game. ( reaching said unit is the problem)
2. These guys are one of the best assault units in the game. Super high initiative, rending( AP 2), fleet, fearless all for 14 points.
3. Brood lord can be upgraded as a psyker. Hit or miss but a iron arm or endurance broodlord is good to go.
So that all being said they still have utility in army. A counter charge unit to watch your Tervigon is a good way to use them as the gaunts move forward.
I think they could also be used as an harassment unit to force the enemy to deal with them on a flank or as a frontal suicide squad.
With more and more infantry based lists I think these guys "can " be a answer only if they get to assault. That being said this is a hit or miss unit.
Here is a 1850 list I came up with using stealer in a semi-balance list:
Tervigon-215
Tervigon-215
Zoansx2-120
Zoansx2-120
Y-stealers x -230
Stealer squad-210
Stealer squad-210
Tervigon-215
Tervigon-215
Gants-50
Gants-50
20-psychic power ( can list tailor vs army "X" with powers )
6 troops ( with more to be generated with tervigons )
ability to infiltrate or outflank troops.