First of all, profession/archetype has nothing to do with pet AI. I have personal opinions about secondary rangers and pets, but that's neither here nor there.
But there absolutely is a problem with the pet AI because it's IQ is that of a turnip. A simple solution would be to have a Guard setting that applies to party members in range. There's no excuse for the companion returning to the ranger in the middle of a battle with your party dying just because itself/master are not in danger and it was not given new command.
Yes, manual targeting works, but that should be for micro-management, it shouldn't be required to keep your pet out in aggro. When it pulls back, it exposes allies/party members to attacks, either by allowing aggro to refocus on others or pulling it back toward the ranger and others. It also means precious seconds of a fight are wasted on transit when the pet could be contributing.
As for the sluggish nature of the beasts, it's more complicated. Making them fast and responsive could cause imbalance, especially given their toughness. They can harass with no investment, so any changes here would need to be PvE-only.