HEIMERDINGER'S ULT.... focusing minions?!

When Heimer does his upgraded turret ult in the middle of a team fight, whether it be on Summoner's Rift or the Howling Abyss, it targets minions instead of targeting the champions that are right in front of his turret. It is pretty obvious that his ult should target the champion(s) in it's range, but I've noticed multiple times that it doesn't. It would be nice if Riot changed it so that it ONLY focuses enemy champions when in range. If there are no enemies in the ult's range, then the turret does nothing. It is very frustrating to ult in the middle of a fight, die, and think its okay because your ulted turret will pick up a kill or two...only to watch an enemy champ walk away with 10 health while your ult is just chillin' taking out lane minions. To be clear, I'm not saying that it never targets champions. It just doesn't stay focused in the middle of big fights. Example: it will hit an enemy, then a minion, then a different enemy twice, then finish off by hitting another minion. I have lost kills because of this. It should always focus champion targets (and towers/inhibs for those who use it to take them down faster).