So the Sentinel has how much Legendaries now? 4? 6?
2 from Zarpedon, Longnail, Black hole? And all the others it don’t drop.
If I farm it, do I need to get the raid version, or can I farm the normal for its legendaries?
I’ve only seen orange from the Invincible version.
The sentinel also has the classmods
I would venture to say that you should always(if you have the moonstones) play the Raid version of the Sentinel. In my personal experience, I have always received a legendary weapon as well as a skin/head on every run. Seeing 2 orange glow’s is awesome!
He is tougher, but worth it. 
Edit: you can farm the non-raid version of the sentinel. However, he doesn’t have the high chance of legendary drops like the raid version does. That being said, I have received several legendaries from his non-raid version. you’ll just be putting in more time in my opinion.