Redirect - but be cagey about it. Don't throw them away just because you can redirect; make sure that everything else is in position. If you don't need to redirect right at that point, then hold them back.
I can give you two excellent examples of how to use Skink skirmishers and how
not to use them, both from my last game. The distances and positioning isn't exact as I am working from memory, but you get the idea.
Example One - Bait and Switch
So here we have the left flank of the battlefield. There's some other stuff going on but these three units are key: 6 menacing looking Skullcrushers, one unit of Skink Skirmishers, and a unit of Skink-Kroxigor. Although there are 3 Kroxigor, the unit would get hammered by a Skullcrusher charge. In my first turn, I have re-positioned the Skinks so that they are slightly further forward and at a better angle to redirect - but I haven't pushed them up to bait just yet. I want my Skroxigor and the Skullcrushers in a slightly better position before springing the trap. With a big, monster-killing swamp in the middle of the battlefield, the Skullcrushers have little choice but to heplfully run straight forwards.
In my turn 2 the Skinks run into position to pull the Skullcrushers off at an angle. Being Frenzied they have to charge and have to overrun, which...
... Leaves them perfectly open to a flank charge! The Kroxigor kill two 'Crushers and a handful of Skinks die, but thanks to static CR and wounds inflicted I win the combat, the 'Crushers fail a modified leadership test and promptly flee off the battlefield. Not even a problem.
Example Two - How Not to Do It
Here's the right hand flank after my turn 1. Again there's some more stuff going on but I've kept the critical pieces. Unlike my example above, my positioning here is all over the place: the Skirmishers have gone forward almost their full 12". They're in position to redirect the Gorebeast chariot, but they are equally open to a flank charge from the Disco Lord. If he takes it he can be into my battleline in a heartbeat. I've put the Scar-Vet there as bait for him, which he takes, but this is turn 1 - I've no need to take risks like this so early in the game. All I've done is exposed my Scar-Vet and given a relatively slow moving unit an extra charge and overrun roll. Moreover, look at the positioning of the Forsaken - unless they want to go through the Forest, they are either going to be blocking up the chariot's slower movement, or will be blocked by the Chariot themselves; either way by offering a charge I am giving them an avenue to advance through that they wouldn't otherwise have.
In fact, that's exactly what happens - the Scar-Vet gets charged and killed by the Disco lord, and the Gorebeast Chariot charges in to the Skinks with the Forsaken moving in to the gap behind. But I make another miscalculation: the chariot doesn't do quite enough damage to beat the Skinks steadfast; meanwhile they are blocking a counter charge from the Cavalry, who end up taking an Eye of the Gods buffed Disco lord and doing nothing the rest of the game until being killed to a Saurus.
If I'd been a bit more cagey and held back initially like I did on the left flank, I could have used the time to get into a better position to set up the counter-charge, forced my opponent to make a difficult decision with the Forsaken and had an extra magic round to deal with the Chariot/Disco Lord. As it was I practically threw away all three units here just by placing the Skirmishers (and Scar-Vet) unnecessarily far forward.
Incidently this game was against the new Warriors book and I have a full battle report, alas with no pictures, which I can put up if there is sufficient interest.
