You could easily replace the spell casting portions of the Snag table with a more randomized, deadlier table for spell failures.
One possibility might be to grab the spell failure table from something like Rolemaster and use it. It is percentile, so perhaps failure means you roll 2d10 on table, if you earned a Snag Point, you rolls 2d10 and add 20, 2 Snag Points is add 40, 3 is add 60, plus you make this roll be allowed to explode as well., so you can get even higher within the 1-100 range.
That right there would make magic MUCH more deadlier.....