If you go 2handed spec you literally never attack with your right hand weapon - you slam and hit with your 2handed weapon always. If your target is not stunned you switch to s/s to increase your defenses and wait for the attack timer to before you attack with your 2handed weapon again. Therefore, I don't see the point in high slash spec because you will not use those styles ever.
I had the following spec for solo play because I think weaponskill from 2handed spec is more important than reaching 52 composite spec in slash. This should work very well for solo and small man.
48 chants 42 shield 50 2hand 31 slash rest parry
In full groups you usually play as a peeler and I suggest getting as much block as possible for guard and 44 thrust for the insane snare style.
I tested this with my paladin and an armsman friend and his polearm. Slash spec no longer reduces variance that i can tell. Here the advanced weapon skills (Polearm, 2hand, etc...) appears to calculate your slash, thrust, or crush spec into one damage modifier that determines your damage. At lvl 45 with 40 thrust my 2hand swing damage modifier was 40% higher than without any thrust spec. Im not suggesting you need 50 slash to cap damage, but it definitely has an impact. With free respecs all the way to 50 test yourself, and go with the spec you prefer. Most recommend 44 2hand, 48 chants, 42 shield, composite 52 weapon, rest parry.