it does seem like a really odd change, i'm not sure what the intent is besides maybe accuracy? In a server that goes out of its way to make it convenient to level and play this seems like an unnecessary inconvenience for focus pulling (unless you're a necro)
When anyone in your group gets agro...any baffing mobs will randomly select a group member and make a bee line to them. This is how it suppose to work.
Previously if you sent your pet in ALL mobs aggroed directly to the pet which is wrong. This should now be fixed...if this is what you are referring to.
The only reason I can think of for this change is to encourage grouping of tanks. This isn't normal FDS pulling behavior, but it's their server and their rules.