"The Viable Build"

It's exactly what it sounds like. Aside from a few alternatives in Level 10 and 20, and swapping The Master's Touch to Arcane Charge for safety, this is the only build you should be reasonably picking.

"The Best Build"

Hey, it may be the best, but it's too hard to play well to be viable.

...that, or i'm just memeing you, and I just picked out all the worst talents for each tier. Choose what you want to believe.

Level 1

Stable Portal adds another 3 seconds to how long portals last, for a total of 9 seconds. Once you get Quickening at 13, this will make it so you can have a portal up quite literally 90% of the time.

Portal Mastery is pretty pointless, and may end up just wasting your time.

Raven's Intellect is also pretty pointless, since you'll rarely go OOM unless you keep missing all your rifts or something.

Level 4

Mage Armor relies on your teammates actually going in your portals, and even then it's only really good against a team with heavy AA damage.

Bird's Eye View gives a very significant buff to your spotting. Vision is always a great asset to have.

Dust of Appearance is a super niche talent to pick when there happens to be an extremely oppressive stealthy on the enemy team that's giving everyone a bad time. Even then, Bird's Eye View will give more general value.

Level 7

Arcane Charge should only be picked when you absolutely know that you won't be able to get your The Master's Touch stacks, for whatever reason.

The Master's Touch is almost always required, because it gives such a big boost to your tickle power. It might as well be a baseline quest that you can only start 5 minutes in.

Arcane Explosion doesn't do enough damage to warrant it replacing the two Q talents in this tier.

Raven Familiar is the best talent in the game, hands down. It's so brokenly overpowered that the community has taken upon themselves to completely stop using it, in the name of game balance.

Level 10

Both heroics are great, but Ley Line Seal is the marginally preferred pick. If there's a diver on the enemy team, like Genji or The Butcher, you might be better off picking Poly Bomb.

Level 13

Quickening halves your portal cooldown, from 20 seconds to 10. As stated earlier, this effectively gives you a 90% portal uptime. More playmaking potential, more escape potential, etc.

Astral Projection is decent, but you probably won't get as much use out of it than a halved cooldown. The base portal range is already more than enough for an easy escape, most of the time.

Winds of Celerity is also pretty okay, but you aren't much of a split pusher so you won't be needing it as much as the 2 portal buffs.

Level 16

Circle of Protection will give you zero value if the enemy team only tries to burst a hero at a time (in other words, any competent enemy team will make the talent worthless).

Enduring Will isn't a significant enough buff to survivability unless you find yourself casting shields too early.

Reabsorption is a fantastic talent, and even has the potential to heal you or your teammate to full health if the enemy team really wanted to burst the shield target.

Level 20

Glyph Of Poly Bomb is only effective on grouped up players, but if the players are grouping up, you'd be getting more value out of Ley Line Seal anyway. Avoid.

Medivh Cheats! is the go-to talent if you don't need the minion cleaning of Guardian of Tirisfal.

Guardian of Tirisfal is a decent thing to have, especially if your team isn't the best at waveclear.

Arcane Brilliance is too niche to be a viable pick compared to the other talents.

Invisibility is similarly very niche and tends to be worse than others.