Ok. So the warlord was just: "if there was a martial healer that recovers resources on a long rest, there is also a martial that cries for long rests and so it is not only spellcasters?
I guess, if you play the game where spellcasters don't conserve their resources and always go nova and always get the chance to long rest whenever they want, then spellcasters will always be ahead of martials.
If you play the game where encounters can happen even after spellcasters have gone nova, martials are not that bad off.
In my experience, martials will need a lot of healing. But in my experience, as
@Zardnaar already said, the healing needed is greatly reduced if spellcasters controp the battlefield. And I add, that if spellcasters also sometimes mix it up in melee and take some hits, healing surges take you a bit further.
One problem I see is that many people think, that range is always better, because you stay out of melee. But our group noticed fast that if noone goes into melee, everyone can end up there. And if only a single person is the front line, that character eats up too many healing resources.
Is spreading the hurt the most optimized tactic? Probably not. But it is way more fun for us than going nova->rest->nova->rest. Which actually only results in an arms race between DM and players.
A DM that creates tension and uncertanity when combats can happen, and also uses varied enemies and tactics, that can't always be taken down by cookie cutter combos, will be able to balance spellcasters and martial easily.
That was one of the first lessons I learned in 5.14 and it works even better in 5.24.