|Everybody will be shooting at the Warhound titan, I feel safer already...|
This is one element most 40K tactics video or blogger dont really talk about... The element of Aggro..
Actually in some way Aggro is term used in the PS3 game Army of Two. The idea of the game is the one with the biggest gun and loudest gun will generate Aggro. So when that happens all attention is diverted to that player leaving his teammate free to maneuver around for a flank.
Although Warhammer 40K isnt a real time game.. but in a way this application can be applied.. Example of unit with high aggro is a Space Marine Vindicator. A 24" STR 10 Ap 2 Pie template unit just it appearance alone already strike enough fear to your opponent. Almost alot of stuff even spread by cheese generate high aggro.. like Nob Bikers or a Falcon with Fire Dragons, or Land Raider with Assault Terminators.. These guys will generate alot of attention and will usually be rarely left alone.
So your opponent will do its very best to knock it down or at least avoid it... So a unit with high aggro can grab the attention of your enemy.. force him to divert his best forces to engage your high aggro unit.
Sparing your other unit from them like troops so they can hold objective while your opponent dukes out against your high aggro unit.
Understanding the Aggro level each unit in an army can help anticipate how your enemy respond to your army. So in a way you can always use it to your favor... like e,g.. Sending your Land Raider with Assault Terminator foward to the enemy while diverting your Marine in Rhino to secure an objective. So hopefully your opponent will panic and divert everything to take your Land Raider. Leaving your troops free reign on the objective. So even if your Land Raider and Terminator perish... You get to still hold the objective for another 1-2 turns..