Is using a stranger plant worth it?

yes, but not scrolls

You mean for combat? No, it isn't a terribly powerful fighter. It's outdone by the spirit cobra, smoke devil, spirit kyatt, and karamthulhu overlord, even before you can upgrade to higher level familiars like the titans. This is mainly because it sometimes does a little poison spray thing in place of its usual attack that has a max hit of like 2...so its damage output is decreased, even though its max hit with its normal attack is 12 instead of 10 or 11 like the lower level ones I've mentioned.

 

 

 

It's worth making the pouches for summoning experience if you're under 74 summoning, and I believe it's also worth buying the pouches to swap for shards (might wanna double check that), but that's it.

For farming it is OK. I used it recently to do a round of torstols as I needed some zammy brews (which never buy, neither do torstols)

 

 

 

The only downside is you lose the extra 12 spaces a Terrorbird gives, which is a godsend for farming.