I fixed a bug with valour about a week ago that should solve the issue of people not getting valour with 40 points when the rest of their team gets very little. That being said, this won't change the OPs concerns. The problem is the siege gamemode itself (or alternatively, you could look at it as the valour requirements being the issue. Really it's the same thing, just two different perspectives though.) Because people can respawn, it's much more forgiving. Players are easily capable of getting 20 or 30 points in a singe round, whereas in battle, the average score per team tends to fall somewhere between 5 and 10. This just makes it that much more difficult to get valour.
Few people getting valour on Siege is nothing new, the month or two where people were able to get it 3-5 players as a time on siege, was an irregularity that wasn't exactly intended.
I've thought about changing the valour requirements for siege, but I concluded that for the most part, due to not having score rewards for objectives (which were previously deemed to be a poor idea), valour conflicts with core mechanics that make siege what it is. To be honest, I'd rather remove valour if we're not to grant score for objectives (which is hard to do.) Valour is mostly harmless though, so there's no point really in removing it from siege.
