Kill the transport and then avoid them. They only have a charge range of 12 inches so you can avoid them fairly easily whilst you whittle down the rest of his army.
No offence but, no. I think you need to do the opposite.
I fight a SM player who fields Vulcan and assult terminators and although he does not use a land raider the squad must be destroyed.
Ranged weapons to an extent are good, but if you're using obliterators i'd only shoot at them if there was nothing else worth shooting at, with a 2+ save and 3+ invun it's not worth it. with high ap shots you're not going to force enough saves and high ap shots don't have enough impact.
First things first, we need to get rid of the land raider. he's definately going to charge that thing straight towards you and in a way such that you can't ignore it. Your two main options are to either destroy it first or give him bait.
To shoot it down you'll need melta or ordinance, vindicators can do very well and serve as a good distraction tank. deepstriking terminators with combi-meltas should do it as long as you have an icon nearby. PM riding in rhinos can pop it through the firing port and so on. I wouldn't reccomend using lascannons since it's 6's to pen and your oblits probably have other high priority targets to shoot. Although don't try to destry it in cc. only your dp's have a good chance at killing it and he'll just get counter assulted which is bad.
Currently at 2000pts i have all of the options i mentioned above which allows me to deal with multiple land raiders with a little luck (you always need a little when facing one).
The second option is to use bait, eg a PH squad in a rhino with meltas. just run up in front of it and start shooting, he's scared of the melta and will destoy the rhino and then assult the pm's inside. either way they must get out of the raider.
Once this is done the single best way of killing them is through cc. prefably assult him with multiple units such as demon princes and khorne berzerkers. Kharn is a very good choice for this and i loved using him in exactly this situation but remember he's not immune to instand death so only use him if you're confident that the squad will be destroyed before they strike back.
A simble rule of thumb for me is for 6 assult termis or less use 1 dp and a squad of at least 8 berzerkers (my champ has a p/wep rather then p/fist which i explained in a different thread but it's basicly because i don't want the berzerkers charging vehicles hence i don't need it).
Now if you use kharn that would replace a dp so in my opinion kharn and a squad of berzerkers on the charge will kill the squad. if it's a rather large assult terminator squad or has a dangerous IC, then i'd assult with another berzerker squad and/or another dp, preferably one with warptime. The best way to ensure all these squads assult at the same time is to use rhinos and have them near the land raider when you start shooting at it (but don't disembark before the thing is destroyed even if it means waiting a turn. you don't want your guys in the open to find out you didn't destroy it in the shooting phase) or to have your rhinos nearby to your bait unit since you can disembark, move then assult providing the rhino did not move.
Either way the best rule of thumb is to attack it with melta or ordinance to destroy the raider and assult the contents. if you're having difficulty destroying the raider then set up a counter assult for when he does get out.
Good luck