Let's say that some chap has a nice vitasuit or plate mail with lots of heart trinkets. He/She's a tank, right? Not really, because monsters attack whoever they please, usually the first knight who enters their "vision" area. A change that would fix this is have monsters have priority over the knight with the most health, not percentage wise. Here's how it could work:

Let's say you have a gremlin thwacker, and four knights. One of those knights has the equipment described above, so it attacks that knight, and FOCUSES on them until the knight runs out of range (is that even possible or do they keep chasing you no matter how far you are?) or falls unconscious. The gremlin does not switch targets every time it reduces the knight below the health of another. If a knight with less health were to enter the gremlin's field of view first, it would attack and focus that knight, not the highest health knight, regardless if the tank knight enters it's field of view later or not. If a knight were to attack the gremlin while the gremlin is focusing on the tank knight, it would switch to that knight, the one that caused damage last.

This makes guardians and tanks more viable, and can be sent ahead to draw attention. This also helps with trojans, who tend to follow any old knight it wants, and switches now and again.

If any clarifications are needed, just post.