Easy way to kill a fernando is to get behind the enemy and hit him from the back which will force him to turn around leaving him vulnerable to champions that were in front of him before,but you will have to be careful of his allies.
Ruckus' average position relies on what legendary card he picks. If he has Recycler, he'll often be to the side of the objective, if he has Flux Generator he'll usually be on the objective. If he has Aerial Assault he may be above your team.
You can counter a lot of high damage ult or abilities with obliterate or your ult. Maxing out at 80% damage reduction if done correctly with cards and timing.