I have not really had much trouble with wiper speed on any of the LUVs I've owned. I have more trouble getting them to track right and keep from skipping off the glass when I'm doing 70 in the pouring Oregon sunshine. I have been driving a LUV since high school though, so maybe I'm just used to the speed thing. Personally I don't like my wipers flapping back and forth 3-4 times a second, so I don't even run mine on high speed.
I posted a tip a while back that might be some help though,
Fixing Leaky Wiper Shafts. It covers greasing and resealing the part of the shaft that the the arm hooks to. A little rust there can go a long way to slowing things down, not to mention the massive amount of water the leak can collect on your floorboard.
You might have something of an electrical fault going on, like a weak battery or alternator. If you've seen any other signs of this like dim lights, low speed on the heater fan, or sluggish cranking speed from the starter you might want to get the bat and alt checked out. Most auto parts stores (Shucks, Autozone, etc) and just about all battery shops will have some sort of free test they'll run on both for you.