Yet another house rule
IMC, I set the DC to tumble around someone at 10 + their highest attack bonus. The DC to tumble through someone is 20 + their highest attack bonus.
This does a few things: It prevents me from having to make yet another roll (as others have suggested be done with Ref saves). It keeps me from having to figure out the critter's BAB (which some varient tumble-rules demand). And it reflects the combat prowess of the opponent. It also scales really well with character level vs. monster attack bonuses. At 8th level, PC's can have roughly +15 to their Tumble checks. A quick search of CR 8 monsters shows that they seems to have attack bonuses in the +12 to +17 range.
The problem I have with TV's suggestion is that it doesn't fit my campaign very well. The only character with Tumble usually has an AC of 24 or so. He's maxxed out his tumble check at about +15. If I understand TV's rule, then this maxxed out tumble score will only benefit the character at all 50% of the time (if he rolls a 10 or higher). And even when it does benefit him, it won't do so by a whole lot.
We came up with a very similar rule to TV's, and eventually decided not to go with it. Which is not to say it isn't a good rule...it just doesn't fit for us.
In addition to all this, I also rule that if you don't hit the high DC for tumbling through an opponent, you just can't do it (in addition to provoking an AoO, if applicable). This prevents the whole "I have 1 rank in Tumble, and you already wasted your AoO! Pbbthth! I walk through you, ghost bouncer!"