Some of the weapon properties are very fiddly in play and if released as is I could see them being annoying to track. Namely sap, slow, and vex. Those properties inflict "until start/end of your next turn" types of conditions, plus not only that but also "next attack" -- that's a double whammy of fiddly tracking. The issue here is that these properties are applied on every single attack, which is often 2 attacks, sometimes 3 or even 4 (even in tier 2 with action surge or haste).
Imagine a party with two PCs with access to mastery properties, and they use Sap and Slow weapons. Imagine a fight against 6 enemies, and in one round PC1 inflicts Sap on two enemies, and PC2 inflicts Slow on three enemies, two of which also have Sap. Now you're tracking:
- 1 enemy has disadvantage on their next attack (not all attacks!) but made before the start of PC1's next turn
- 1 enemy has -10 speed until the start of PC2's next turn
- 2 enemies have disadvantage on their next attack made before the start of PC1's next turn, but also -10 speed until the start of PC2's next turn (note the two different PCs, aka two different initiatives)
And variations of this could happen every single turn. It's rather fiddly.
The other properties are fine.
Edit: Actually Topple is a bit annoying as well because you're rolling a saving throw with every successful attack. It's a pretty big increase in the number of rolls, which slows down play.