Well to be fait the skeleton quest in Horizon is hard even on solo level. Altho at your level you should be able to do 2 stars.

You are an archer but did you level ccon or thm to get at least the level 1 cure or sacrifice to help healing yourself? It's like level 8 I think so it takes about 30min to get it.

Aside from that, try to bind one of the targets when they come in pair and focus on one.