I never thought of Jen and Kisha as weak, far from it! I don't blame the other teams for not wanting to compete against them in the final 3. Those girls can run!
Well Tammy & Victor use of the U-Turn was one of the smarter uses of these sort of tools (no matter all the bitching at sucks).
1st Victor & Tammy (the last time they absolutely knew) were only ahead of Kisha & Jen.
You only use that sort of tool on people you believe are behind you.
2. They understood that the final leg has always had some serious running in it. So then get rid of the fastest team.
3. The last few seasons have ended in a brain task, I am sure they feel that here they have no direct competition.
So its aboslutely logical to use the U-Turn on Kisha & Jen, in fact either other choice would have been stupid (unless at some point Tammy & Victor were aware that they had passed Margie & Luke and Jaime & Cara).