Ok, the increase from 1% to 2% success is not the same as the increase from 50% to 100%. Yes, the increase in both cases is to double the chance of success. However, if you look at it from the other side, considering your chance of failure, on one case you have a drop from 99% to 98%, and on the other you have a drop from 50% to 0%. One is just over a 1% decrease, and the other is a 100% decrease.
As for the original topic, the Chaos team I started recently (having not known how to play as them... though to be honest I didn't know how to play as any team, other than High Elves.

) Had 2 TRRs, FF8, 8 Beastmen, and 3 CW's. Looking back I would've rather had more TRRs probably, but the team worked out well, going undefeated in it's first... 8 games or so, I can't remember. The first game I lost, the luck was slanted so badly against me, that by the end of the game my opponent was dodging mummies and picking up the ball with them to stop me from scoring, and I was rolling triple-skulls.
The luck was a bit odd too, I averaged over 4 casualties per game, but only had about a 25% ball handing success percentage. At one point my team had failed 12 straight attempts to pick the ball up, not in anyone's TZ.
I find the advantages of a Chaos team to be a bit more subtle than most... the ST4 Chaos warriors are useful, despite being expensive, and is the most obvious advantage against teams that only have Strength 3's. The two similiar teams I'd compare them to, are Lizardmen and Orcs (with BOBs and Saurus' matching up with CW's). Over Lizardmen you face the disadvantage of them having 6 ST4 players instead of 4, all who move 6 instead of 5, but you don't have the liability of the weak and injury-prone Skinks. Over Orcs you have the advantage of Ma5 vs Ma4 on your CW's vs the BOBs, and Ma6 over Ma5 on the linemen. And the AG3 vs AG2 on your CW's, though it generally won't come into play because they'll be busy bashing, if the ball happens to land near one, within scoring range, you'll be thankful for it....