[Saryn] has a great base kit that is able to deal with almost every type of content in the game. This build focuses on the melee aspects of her kit. We subsume an additional buff to push her damage potential further.
Roar is chosen because it triple dips with Toxic Lash and increases the damage of the rest of your abilities. Warcry is a good option for more defensive roaming builds since you slow down enemies. Ensnare is a great CC tool that also allows you to blender groups of enemies with your melee.
Molt should be replaced if you're choosing a subsumed ability. It's fairly weak at pulling aggro in most content and the speed boost doesn't last long enough to cement itself as a solid ability.
Efficiency is extremely low on this build as you're primarily using your energy for buffs that have decent duration and Spores which shouldn't need to be recast often. [Blind Rage] can be replaced with [Transient Fortitude] if you're having energy issues.
Duration can be traded for more Efficiency or Strength but your energy economy may suffer. It also makes your Miasma no longer last 10 seconds in ESO. Some people don't like using any Duration at all as they can just refresh their abilities. [Primed Continuity] is on a depolarized slot so that you can swap it out for any other mod to suit your playstyle.
[Venom Dose] is a flex mod that can be replaced with any augment or Augur set mod of your choice.
[Rolling Guard] and Shield Gating should be plenty of survivability in most situations but you can run [Vitality] or even [Adaptation] to increase your passive defenses.
Arcane Strike is primarily used for it's synergies with Toxic Lash but any other arcane can be run to suit your playstyle.