Well, months passed, I eventually forgot about this and made a big break of Minecraft and started playing other games (even got a ps4 last year). However, a few days ago, I decided to dug up my ps3 to play some older games. I turned it on again and the first game I grabbed from the shelf where I have my old ps2/ps3 games was Minecraft PS3 edition. After downloading all the updates I missed, I launched the game, revisited my old building worlds, etc. Everything was still untouched since I made a break of Minecraft a year ago: My houses, buildings, farms and... Connection problems. Yes, could you imagine my face when I tried to connect to Battle minigame and still have the very same issue I had one year ago? I though that one of the several updates I had to download when I turned PS3 on would fix this problem, but it didn't.
Btw, I tried to host a match myself, but no one came in after a long time waiting. And I managed to join another minigame, so the problem seems to be with Battle itself. And yes, I can play other games online, so it's not from my internet.
I hope someone can help me this time. I would like to try this minigame.