the problem is that 5E lacks a "Tank"
Circle of the Moon Druid and Bear Totem Barbarian would like a word. Aggro is a thing. If the low-INT creatures are going for the back line after a raging fuck machine runs into them - that's a DM problem not handling aggro realistically. If the high-INT creatures/people can get to your back line that's a tactical or party composition problem - or not - just because they're the back line doesn't mean they shouldn't feel danger. Neither are problems with 5e lacking a tank. Tanks are tanks in 5e. If you want lockdown or control, you can get that elsewhere.
