Today we played champion and we don't get it... It is an advantage if they take out your champion afte he/she has attacked as you can get a new champion inmediately and attack with him and get the points again. There is really no incentive in killing the opposite champion, actually there is little incentive to attack someone else with other than the champion, specially in the 2d-3d turns when your opponent still has 2 reserves in case you manage to injure 3 enemies.
And about the VIP challenge, it is like you can chainkill enemies easily and get a lot of points in your turn, I kill the VIP, I call VIP on other enemy I can kill this turn... it is ridiculous.
What do you think about these two challenges?
They both require different tactics and approaches other than the brawl mentality. Others attacking in champion isn't useless, unless you have brawl mentality that says "if it's not void, it's a failed attack". With that in mind, then other characters attacking doesn't matter. But, in champion, water results are one of your best friends. You use them to bring targets to the champion. Board positioning and maneuvering the enemy is a very important part of that scenario that doesn't exist in brawl.
Assassination is similar, in that, if you come at it with a brawl mentality, you will not do well. In assassination, you need to protect certain targets, but you also need to have some foresight. In brawl, you can scatter your ninjas like ants after their kill was kicked over and go after whatever looks easy in the moment. In assassination, you have to look at all your ninja as the next potential target. keeping tighter formations so you can fill in gaps, and run interference on the next potential target at any given time is important. Breaking formation just to attack some rando will help your opponent far more than it will help you. And, assassination is one of those scenarios that could be very high scoring in general. Some scenarios end up with higher scores than other scenarios just naturally.