I'm assuming you're using a ranged weapon with your companion in which case they only roll dodge when their focused target comes close into melee, they ignore all other circumstances. It may sound like a bad idea, give them melee weapons like Two-Handed or Dual-Wield, while they will stick close to their target they will also use their roll dodge when they drop to 50% health or lower improving their chances of moving out of bad ground crap.

If there are multiple enemy targets in the room, you can force them to move as well by commanding them or heavy attack another enemy to reposition by having them run to another target, this is less effective with you guessed it a ranged weapon. Once they're out of the bad ground crap and are in a better position you can redirect them back at the previous target. You can also command them to stop attacking and run back to you which does the same thing if there is only one target in the room, harder to reposition them this way, but still gets them out of bad ground crap instead of waiting for them to do it.

Build them to be like a tank without being a tank. At least 6 items with Vigorous, the rest with either Quickened or Bolstered. If for whatever reason you're using Telvanni Efficiency which isn't bad for Arc 1 maybe 2, you can go with more Vigorous. The more health they have the more time you have to move them out of bad ground crap or survive big hits.

I prefer Sharp-as-Night healing build, Dual-Wield and 12 Vigorous, your choice of armor type. Snow Squall first slot heals him for nearly 30% of his maximum health and has a heal over time. Fungal Forage second slot always heals himself, you just need to stand in the direction he is facing to benefit as it's a cone type ability. Sleetmail third slot gives you a source of Major Resolve (5948 Physical and Spell Resists) if you don't have one or miss recasting it while also reducing his damage taken. Skeletal Aegis fourth slot is 30% max health damage shield for himself and 6 second window for 50% max health damage shield for you. Fifth slot you can use whatever you want, I suggest Petals of the Hunter, Crimson Font, Infest (Minor Vulnerability), Char, or Cold Snap depending on what you want him doing.