Weakness Policy conflicts with Burst Balloon. You still want the extra damage in the Darkness match more than the zero weakness on Trevenant.
I think it really helps, but let's do math:
Trev Break with weakness policy stands:
- 6 Unmuscled oblivion wing = 6 turns of silent fear = 180 damage
- 4 Muscled oblivion wing = 4 turns of silent fear = 120 damage
- 2 Unmuscled oblivion wing + one evil ball of 4 energy in both pokemon = 3 turns of silent fear = 90 damage
- 1 Muscled oblivion wing + one muscled evil ball of 4 energy in both pokemon = 2 turns of silent fear = 60 damage
- Mind Jack is circunstancial so i'll not refer to it, but you can easily control the damage being careful with your bench
So, in THE WORST SCENARIO, Trev Break without weakness will give you 2 turns of damage spread, needing just one more silent fear to be capable of knock out every single pokemon on your opponent bench with wobbu, also keeping your burst ballon for the late game. On the other hand, IN THE BEST SCENARIO you'll be capable of knock out even an Yveltal ex only attacking with one or two Trev Break.
Trev Break without weakness policy stands:
- 3 Unmuscled oblivion wing = 3 turns of silent fear = 90 damage
- 2 muscled oblivion wing = 2 turns of silent fear = 60 damage
- 1 unmuscled oblivion wing + one unmuscled evil ball = 2 turns of silent fear = 60 damage
- 1 muscled oblivion wing + every single othe atack of YZG = 2 turns of silent fear = 60 damage
- 1 evil ball, 1 pitch black spear, etc...
So, without weakness policy, your best scenario is having 3 turns of your Trev Break alive, but appearing as the most likely of you having to promote a Trev Break every two turns to maintain the lock and the damage spread. This situation, even with the damage output bonus that gives 4 burst ballon seems very clunky, difficult to maintain and also very easy for your opponent to play around, he can choose when or not attack, and your burst ballon will end hitting mostly baby yveltal or in the discard pile because of the pressure on promoting new trevs.
In my opinion, including weakness policy in this deck is a must and also something very easy to accomplish with a little work on the list and spaces, taking care on not affect the consistency of the essential strategy.