The curent TW reward system makes no sense. If you win alot you will face guilds with higher GP. That part makes sense, you are good so you get better opponents like in Grand arena. But problem is you wont get better rewards for it, with makes no sense. The logical solution to this is easy, both guilds should get rewards from the tier that the guild with the highest GP is in. That way you Will be rewarded for being good and even if you lose you might still get better rewards than you would have goten if you won in a lower tier.
So 300 GP guild vs 200 GP guild, both guilds get the reward from the 300 gp reward tier.