People use some weapons because they notice the buffs, it doesn't mean that unused weapons are bad. They just require you to actually think a bit on how to use them.
There isn't many GvGs atm, and thus the meta is not evolving completly, people do not want to risk using a "non meta" weapon and prefer to stick to the current op and not do the theorycraft themself.
You're talking about the 20vs20 GvGs but you don't seem to know shit about it. You can observe changes on compositions and gameplay every 20vs20 GvGs and BA actually had some bows in their comp. Also the weapons used in 20vs20 are not the same than the ones used in 5v5 for obvious reasons.
Why is there changes every GvG ? because the "meta" isn't fixed since there isn't much GvGs.
If the number of GvG goes up, you will actually discover a lot of new comps (as in scrims but for real) and since bow isn't underpowered as you think it will have a place in GvGs.
Just stop being a meta slave and playing a soldier armor because someone told you it's OP, it was actually stronger before the original buff it had than it is now (but oh! surprising! people where not using it?)
You even failed to understand the point regarding the 20v20.
Wake up, there is no "meta", get your head out of your ass, open your eyes, check the logs, you will see every single weapon line being used in GvGs beside Bows.
Yes, read my reply, and actually comment on it, mister meta.