Is there a set location for Skull of Harlon?

The Bone Pits in Act 5, a main area about 2/3rds of the way down the waypoint list

Got one, thank you.

Any of the above build(s) you feel stands out for damage/survivability/enjoyability from the others?

For damage I think the most notable ones are Warlock's Demon Lord and Masochist Thorn Spears. Demon Lord has massive up-front output that doesn't rely on infinite stacking (because it doesn't have that), while Thorn Spears doubles up on infinite stacking which means the rate your damage stacks up actually increases the more you keep attacking a target unlike most other builds where the rate mostly stays the same.

For survivability the one that stands out is the Berserker Non-set Flamewrath + Hydra build because the build's concept revolves around having extreme sustain to be able to maximize damage gained from Balgar's Binding. The other classes also have ways to build into this kind of concept, though I haven't gotten around to documenting those builds yet and Warden's method is due for a big nerf so I'm not sure if she'll still have builds that qualify after that.

For fun factor it's obviously down to personal preference but I like builds with high mobility so Glacial Roll gets my vote here.

Any tricks to getting the Skull of Harlon? Tried running the Bone Pits several times and not sure if the legendary spawns rarely or if the item is a rare drop.

It's a Unique, not Legendary. It's a forced drop so it's there even with Uniques filtered out and filter cleanup enabled but the label won't show up so you might not have noticed it.

Warden - High Ranger Rapid Shot[imgur.com]
Warden - Stormcaller Charged Arrow[imgur.com] (updated)

Berserker - Volcanic Dragon Warp[imgur.com]

Do you plan to update the masochism build?

One of the next few updates might change the behavior to what I was building around before, so I'll probably just wait for that and check if any further changes are needed. In the meantime you can try the suggested changes that I listed in the link, or just build it exactly as shown since it does still work well enough.

I'm new to the game and trying to follow your awesome Glacial Roll Zerker build, but I don't understand why Dragon Within is there because you said it's not actually used....could you explain please? If it's on the skillbar but remains unbound why would it make any difference? It obviously does or you wouldn't have used it but an explanation would be great please.

Dragon Within is used for its "active effect" which only requires it to be placed on the skillbar to apply. Its "use effect" that applies upon using the skill is useless here because simply using Glacial Roll instead generates more rage while also dealing damage and triggering on-hits.

Ahh I see. Assumed 'active' meant when pressed but of course that's what 'Use' means. Thanks!

I am curious how you deal with mana cost for spamming sword dance in your valk build? I can't see it - is it one of the masteries?

Plea's (Holy Aura) active effect grants a large amount of both Health on Hit and Mana on Hit, which is increased by the use effect. This is further scaled by the skill damage percentage of the hit that triggers them, up to 10x the stat sheet total if the skill's damage is 1000% or higher. If you are unable to sustain it, that probably means you haven't scaled up Sword Dance's damage percentage high enough yet. The easiest adjustment you can make until then is taking the Mana on Hit mastery in place of reduced debuff duration (Class Mastery 5th node), then taking Mana Cost Reduction minor enchants if that isn't enough.