For 1v1 encounters you can easily dodge roll out of their projectiles. Walking out of their attack in conventional speed-decreasing armor is not recommended as they are likely to jump towards you as well while they attack, something that makes their projectile trajectory hard to gauge.

Using a blunt weapon like the Frostner will be a good starting point, Porcupine is best for the raw blunt damage stats to quickly take it down.

For 1vX situations you can try to kite them and shoot them with needle arrows, fire arrows are too slow to kill and give them more chances to get tar on you. If you get their attacks spaced out you can go in for melee and then dodge roll quickly after but not recommended for more than 2 mobs at once.

Growths will also aggro other Plains mobs, ideally, you want Lox to fight them as you can not aggro the Lox yourself and have the problem be dealt for you easily.

Also. if you do get tarred then I recommend just dodge rolling and avoiding the projectiles for the next 10 seconds, having stamina mead is very recommended as an emergency measure. Also always have Bonemass in the plains and save them for tar encounters as they are the most unpredictable depending on how far you have to kite them and how many other mobs end up aggro-ed.
Good Luck!