ehhhhhh I didn't want to re-engage but sure, fine. "what about RA?"
Every RA should be carrying trimates at a bare minimum. Dimates too. Monomates yes, though I will admit to often dropping them so I can carry additional garbage because I have a Teampoints addiction.
Will resta almost always help the RA? Yes. Will a zerking RA need constant resta so that they never spend more than 7 seconds on low HP? Probably not, especially if we've established that the "no resta" is because there's a decent HU out there killing the big threats with DF. Also probably not constantly if there's any form of Cast using FT's. And of course, if you get healed before a big wave or a dangerous spawn, all the better!
Both fleshy rangers have their own resta they can use if they feel they need to. ALL rangers should have trimates as an "oh shit here comes something scary" button. If the ranger in question ISN'T constantly zerking, it becomes even less of an issue. Charge arms, baranz launcher, and just heavy attacks instead of specials on zerk weapons (HS, Excal still do good damage even with just Hard attacks.) are all options to play pretty safe. Basic health management is not a "pro" skill. Resta and DF is a "HU and FO" issue because any ranger should be able to pop a tri/dimate or their own resta if they're in danger.
If anything, I find as a ranger that inconsistent resta can be worse than no resta. If I think I'm safe to just turn brain off and spam Zerk Arms, then the fo who was previously spamming resta every 3 seconds stops to do something else, it can catch me off guard and lead to a death that otherwise wouldn't have happened. Constant resta? Maybe overkill, but I'm pretty safe. No resta? Cool, I need to watch the enemies and pop a mate if it looks like I may get hit. But guessing "will I have HP or won't I?" often leads to death when you guess wrong.
(As an aside to the above, I have a near-pathological hatred of Charge like "money as ammo" effects in every game ever. This leads me to playing RA as a zerk-only class, kinda HU lite. I've actually been asked how I can use zerk arms on HUcaseal.... when I'm playing RAcl. Most people don't hate charge like that, so they can play a lot safer than I do.)