Why give any points for a loss on time?
The problem with the current system is that it if one mage is in a losing position, it incentivises them to just cling onto life, and concentrate rather less on winning. That said, being able to stop the opponent from killing them does feel like it should be worth something.
If you awarded nothing for a modified loss though, you just reverse the position, where a winning player then sits back and doesn't need to try and finish his opponent off, just play defensively, and force them to take all the risks.
Both are about as bad. I think the answer is definitely to increase the difference in points between outright wins, and modified wins/losses. I'd favour proportions something like 6/3/1/0 but I'm not sure if it does something screwey with the maths if you don't split the same number of points amongst the players in all circumstances. I suspect it will affect tiebreaks and pairings, and so you may need to do something like 6/4/2/0 which is arguably worse than the current scheme.