Do you already have Minor Berserk? If not Slimecraw is probably better. Do you already have Major Vuln? If not Archdruid is probably better. Thierric has a neat animation but like Domihaus, it's stationary so opponents will tend to move out of its area. Thierric's advantage over Domihaus is that its proc is easier to control with its more limited proc condition, and it's much easier to apply the debuff than Archdruid, at least until the opponent can evade. The use case for Thierric is pretty much:

- already have Minor Berserk (otherwise use Slimecraw)
- already have Major Vuln (otherwise use Archdruid)
- already have really high Weapon Damage (otherwise use Balorgh/Domi/Kena)
- run an expensive Ult or tend to rely on a defensive Ult (otherwise use Balorgh)
- use some AoE CC

So strictly for burst, rather than pressure, that pretty much indicates a build using Colossus, a Weapon Damage 5 piece, and either Oakensoul or Combat Prayer, since you're not too likely to reliably proc Camo Hunter's Berserk if you frontal assault on a Necro. There's some other narrow specs you can cook up that might get comparative advantage from Thierric, but not many given what I've listed above.