Build Depth & Variety

[faint girder]

Let me take you on a thought experiment.

You start playing the game and you pick Storm as your first mastery. You're throwing Lightning Bolt at enemies and smacking them with a hammer. You pick up the modifier Lightning Bolt increases your weapon damage for 3 seconds, weapon hits increase Lightning Bolt damage for 3 seconds.

You're putting points into Knowledge and Storm mastery, giving you some health, energy, elemental damage, the ability to wear mage armor.

You're now getting a bit squishier, and so you put some points into Lightning Shield (Your barrier scales with X% of your Lightning damage)

At some point you kill a boss and get a unique MI shield which has the effect Barrier is now a passive which regenerates over time. You equip it since you don't like pressing too many buttons and it helps you be tankier without timing it.

You end up liking the battlemage playstyle of lighting spells + smacking things, so you pick Warfare as your second mastery. You see in Warfare there is a skill called Shield Bash (Strike in a frontal cone with your shield, dealing 50% of current barrier.) This synergises well with your constantly-on barrier so you start using it as well.

Since you are playing Storm, there is a modifier on Shield Bash "Convert Shield Bash damage to Lightning and make sparks fly out from enemies hit." and you take that too.

Now that you're putting more points into Warfare, you are getting more health and armor from the mastery bar so you aren't as squishy. At the 2nd tier of Warfare you pick up The Best Defense (Remove the damage absorption of Barrier and instead reflect X% of the value when hit.)

You now melt melee/archer enemies, but you struggle with casters. You find a mace called The Silencer (Critical hits deal +30% damage as lightning and stop casting for 3 seconds.) and you pick up a tier-3 passive in Storm called Tempest (Taking magical damage increases your Crit Chance by X%.)

I suppose the general point is - passives, actives, items, modifiers and masteries could have a lot more interesting interactions.

I think the designers should basically sprinkle a bunch of powerful effects and trade-offs everywhere which make you excited to pick up a unique item, assign a passive point or combine two abilities you haven't played with before and even if this results in crazy interactions, it's not a problem since it's a single-player game and overpowered builds can always be nerfed later.

Having a lot of this power in items and mastery combinations rather than synergy in the same mastery also means tons more replayability and on-the-spot build optimising.

[faint girder]

Build Depth & Variety

[paper badger]

I would love to see this!
I think one fundamental problem right now is we have a bunch of effects related to the barrier and dodge mechanics and melee attacks in the "core" mastery.

This makes it awkward to add more interesting, flavourful and FUN effects like you described in the actual mastery trees, since they would essentially be competing with an overlapping set of core modifiers. I hope the devs can be convinced to delete the "core" mastery from the game entirely, and instead implement all of its features in distinct and actually-interesting ways within all of the different masteries.