not going to make any guides in this post, but just a quick run down for what each spec is strong or weak at to give a better idea of what to use and when to use it.

role -ST dps melee, small amount of aoe splash from whirling dervish.
utility- pull that also applies 5% crit debuff that assassin poison has, interrupt, defer death CD
strengths-very mobile, only stand still channel is earthfall everything else can be used while moving
weaknesses- slightly behind vulcanist in ST dps, limited disconnects, no escape once you jump into melee

role-ST dps ranged, strong splash from beacon of the drake and molten wave
utility-5% non phys debuff(same as clinging spirits from clerics), interrupt, flicker
strengths-highest ST dps, very strong burst damage
weaknesses-EXTREMELY immobile, in pvp very easy to interrupt.

role-ST healing spec
utility- full cleanse, reduced damage taken and increased HP on targets healed, flicker
strengths- very mobile, strong sustained healing with a good shield from deluge, decent aoe healing cooldown from the primal avatar
weaknesses-weak tank cooldowns, 30% mitigation with some healing is the only one that will save tanks from high damage, the other two cooldowns are more suited for pvp.

role- aoe dps melee
utility- aoe pull, aoe debilitate
strengths- (i think) highest aoe burst in the game, burst rotation pulls all enemies in and does massive damage, very easy to play
weaknesses- no way to deal with disconnects, weak sustained dps

role- aoe dps ranged
utility-aoe interrupt/purge
strengths- higher sustained dps than berserker, rotation is very forgiving
weaknesses- very immobile, lots of hard casted spells

utility- interrupt, aoe shield beacon, 20% mitigation buff for raid, self reflect,aoe stun, teleport- guarding ally lets them teleport to you.
strengths- super high mitigation, overall amazing spec probably the strongest spec primalist has right now.
weaknesses-i can't think of any, maybe lack of aoe ranged threat?