A Land Raider can be a really tough nut to crack. They are all too common in the current Mechanized gaming environment.
The Land Raiders come in the standard variety, Crusader variant, and Redeemer variant. They are usually packed out with Assault Terminators, which adds to the frustration.
I have been thinking about how to deal with them, lately. I find that ignoring works well. Rather, I should say avoiding them. If I can coax them away from my main force, or away from the objectives, then I feel great. I only need drive around them or away from them with my fast vehicles.
Getting your opponent to commit to assaulting something usually ties up the Terminators and allows the battle to carry on without them. I think a sacrificial lamb is in order. If the Terminators tear through the sacrifice in the first round, then they are hanging out in the open for my Baal Predators to soften them up.
As far as actually shooting at the Land Raider, I use the Assault Cannons on the Baal Predator. With their rending feature, they can achieve an armor penetration value of 15. It might seem like a long shot, but I suggest you try it.
The thing that I do most is avoid the Land Raider. One unit or one vehicle can't cover every objective. Offer your opponent something to coax that rolling brick out of the center of the table, or away from the real action. Then carry on with the game in the Land Raider's absence.