If you are a Space Marine player or not and if you havent heard of this combo then you must be eitier shitting me or been playing with complete losers. As this is one of the power build that Space Marine plays.
Each Assault Terminator can eitier go for a pair of lighning claw or at thunder hammer and storm shield at no cost. So most player will go for mix of lightning claws and thunder hammer with storm shield. So they get a fair balance of plenty of weak initiative 4 power attack and hard hiting str 8 initiative 1 attacks. So got a means to eitier smash lots of weak enemies or vehicles/monster creature or multiple wounds that have only toughness 4 and below.
As for Land Raider it is a popular choice since it the only vehicle that provide transport for the Terminator (or else they have to walk or teleport in) and because of it Assault Ramp so you can drive to an enemy position and your Terminator can assault the same turn it disembark. Most people opt for Land Raider redeemer as it the cheapest than the rest and have the devastating flame storm cannon (Str 6 ap 3 template). As it compliment the Terminators as it can fire it deadly short range weapons and drop the Assault Terminator into combat. Land Raider Crusader are more for people with the desire to take the step futher by including atleast 7-8 Terminator or accompany IC with Terminator Armor. Land Raider is the least pick as it a long range fire support Land Raider but nonetheless it can still do the job. As for extra firepower people will always add a pintle mounted Multi-melta as since the Land Raider is going to be up close and personal. So the Mutli melta its highly likely to be in melta range which player uses the Land Raider machine spirit to crack any vehicles that in the way.
The reason why this build is so popular is because you are combining the best of everything the codex space marine can offer. To start the land raider all round AV14 is one of the tough fess thing to destroy. Also adding the 5ed vehicle rule make it even tougher . Since even you penned it you may roll a 1 and that thing aint stopping. Now we add the Assault Terminator, they have the best saves that money can buy. 2+ armor save overall and 3+ invul save for storm shield wieding Terminators so at a good roll day the Terminator can survive anything that throw to him . Once the Assault Terminator is unleash there is little that can actually stand up to its assault. As Lightning claw terminator can rip hordes army to shreds and Thunder hammer smash Monster Creatures, Multiple wound unit and Vehicles.
However the drawback and hence why call the death star is that you actually focus everything into one basket. Into one big powerful object. So experience player will simply find ways to avoid it or send weaker unit to engage to weaken it then send their best unit to take it out. Also this army depends on that very Land Raider to actually send the Terminator to the war zone. So if by some means the Land Raider couldn't reach to the destination from either a lucky lascannon round or it got immobilize from a fail dangerous terrain. Then the Terminator is pretty much screwed as they have to walk the rest of the journey being expose to enemy gun fire.
The Terminator is generally few in number so any unlucky roll can actually spell fatal to them. As like rolling 3-4 "1"s for armor save from regular gunfire usually mean the Terminator squad is pretty much dead. So at a good roll they are immortal but any loss it face it a huge blow to the squad.
So you are now thinking that this combo sucks actually no it still nasty and dangerous but you musnt over rely on them to win wars. You should consider them as like an high aggro unit( refer to my aggro entry for detail). Send them into the thick of enemy so hopefully your enemy will over commit on taking them down leaving things like your troops far from harms way on claiming objective.
Also you may add other unit to support the Land Raider and Assault Terminator combo like
A squad of attack bikes with multi melta which they turbo boost to the destination ahead of the land raider so now aggro shifted on them as the enemy is force to wipe them out first or else the attack bikes can cause serious damage.
Land Speeders.. as like attack bikes you flat them out first so forcing your enemy to take them out first hence drawing fire away from the land raider.
Devastator.. this can go both way, if the Devastator taking fire then the Land Raider is spare from gun fire for 1 turn. If the Land Raider is taking fire then the Devastator can fire its weapon without taking damage for 1 turn.
So in a nutshell the trick to use this combo is to eitier send the Land Raider to draw fire from other of your unit in the game or you send other unit to draw fire from the Land Raider so it will take less fire which improve it odds of surviving long enough to send the terminator to its destination.
p.s The term Goo list comes from Wong when a friend of ours came up with this crazy as many Assault Terminator in Land Raider as possible. Which all the Terminator is equip with thunder hammer and storm shield. Hence anything that face that many of hammer shall be turn to paste which is like goo. So the term Goo List is born. So it crazy... at a good roll this army is difficult to kill as it has a high chance of survival on anything throw at them. With that many Str 8 hammer it difficult to not kill anything that touches them.