I'm not too concerned about DPS at end game with the addition of the missile reflect debuff on the charge bar. So I think the main concern now is the outlander's survivability as compared to other classes in raids. Of course we have to consider that is supposed to be a ranged dps class which generally means it should not be able to tank like a zerker or engineer.
That's why vortex hex, repulsion hex, and bramble wall are there, crowd control to enable kiting. But, in the synergies environment vortex hex is especially useless. Repulsion hex is okay for trash mobs. Bramble wall is mainly used for proc builds. Now rune vault is fantastic for kiting don't get me wrong, but it's really the only kiting tool that works well for an outlander in synergies.
As for direct survivability, all the outlander has is stone pact and shadowmantle. Stone pact is good but it's hp regen isn't great when you have 20k+ hp and stacking armor isn't too effective at end game especially since the type of armor an outlander will be wearing is not going to have insanely good base armor. Shadowmantle's cooldown is the only problem with it.
Now as for changing up these 5 skills, I really think vortex hex needs the most help. I believe there is a necro spell that is similar to it but you can spawn multiples. Perhaps that would make it a decent choice for a build.
Repulsion hex and bramble wall don't necessarily need to be changed. Maybe slightly buffed but meh, they do what they're supposed to do.
Possibly only upping the hp regen a bit on stone pact is all it needs. Or changing the applied buffs to be bonus DR or life steal or some other nice defensive stat.
Shadowmantle would be fantastic if it had a 10s cd and the values were lowered to accommodate this.
Also, a side note. There are a few useless skills in the outlander trees for synergies. Along with vortex hex, there's bane breath, tangling shot, glaive sweep, shadowling brute and flaming glaives (only a little).
The outlander pet build will never work in synergies the way it is now. Simply not going to happen which makes bane breath, shadowling brute, and by consequence shadowling ammo and death ritual hardly used. To it's credit, shadowling ammo is okay since they become little aggro meat shields for trash mobs sometimes.
Glaive sweep's casting time and short range are awful. Perhaps making it a cone aoe with some decent range could make it viable.
Flaming glaives has awesome stats but is so unreliable that it's not worth it.
Tangling shot just doesn't warrant it's use in synergies especially since it will hardly ever work on a boss.
Anyways, that's my two cents! Thanks for looking at the outlander some more Salan, I appreciate it.