I mean there's probably hundreds of thousands of variations of martials. I don't think it's very meaningful to say 'aha, one martial out of all of them can do this thing'. My use of typical is meant to carve out space for that kind of exception while still maintaining the ability to generalize.
IMO. We either talk in generalizations to some degree or the terms martial and caster becomes meaningless themselves.
I think it is very difficult to come up with a generalization that holds up in play consistently in a one shot. I think it is impossible in a campaign that covers multiple levels with all sorts of random magic on hand that greatly skews this.
It's really easy to build a survivable caster though. And without having to sacrifice very much.
1. You inherently have ranged options in a game where many enemies are either melee only or vastly more dangerous in melee.
2. You can easily level dip for armor if you don't have it.
3. You can get the shield spell via magic initiate origin feat, or worst case via single level multiclass.
4. You can use a few spell choices on various mobility, defense, summon and control spells to aid your survivability.
5. You can often maintain a strong control spell (either precast or cast on round 1) and spend the rest of the time dodging, while still having a large impact on combat.
And of course there's options for even tankier caster builds.
Melee focused martials though typically have to make significant sacrifices in order to layer in strong survivability.
1. If they want really good AC by taking a shield they give up alot of damage potential and possibly ranged potential as well.
2. They still need a way to handle enemies wanting to maintain range (either mobility, a servicable ranged attack, etc).
3. If they want high damage they typically need a feat, but their defensive options also come from feats.
4. A large portion of their damage comes from abilities that have offensive and defensive options. Reckless attack, battlemaster dice, smite spell slots. If one plays more defensively this even further tanks their damage.
It's very difficult to build an effective martial character focused on defense.
I agree on making a tankier caster, but the part about the martial is not true IMO in 2024. The martial has the same dip options available as the caster and both better and more feats to accomplish defensive play and they also have weapon masteries that substantially boost damage or defense.
Any martial with heavy armor can be at 24 AC with a reaction at level 5 without using any spell slots at all (plate, shield, defense, defensive duelist) and they can be at 23 with medium armor. That is before any magic spells.
The Monk ability Deflect attacks is extremely effective in play. Combine this with a Ranger, Fighter or Rogue for nick(dagger), topple(staff) or sap (spear) and combine it with the grappler feat you are freaking awesome in combat.
There are numerous ways to play this and the character can go either way - strong offense or strong defense and you choose in the moment. I have this in a Monk-Rogue I am playing right now. I have nick and sap with dagger and spear respectively. Opening up against a new opponent and I will throw a dagger close and make an unarmed strike and grapple with "punch and grab" and then nick with a second dagger at advantage and with sneak attack if the grapple lands. Then I use my bonus action to knock the guy prone. If the unarmed strike-grapple doesn't land I still make the nick attack and then use FOB to try to grapple the guy and knock him prone. If everything lands I did 3d8+1d6 damage and the guy is both prone and grappled, and I can move him at my full move speed. We have a houserule that you can't use nick or light weapons using only one hand. If we were playing RAW it would be even more effective since I would not need to throw the first dagger, I could punch first and try to grab making both the next two dagger attacks at advantage with one hand.
If the guy is just grappled and not prone at the end of all that, next round I will hit him with the dagger on my second attack with sneak attack and then Sap him with the spear. Then if I think he is near death I will let him go, nick him and use a couple unarmed strikes against him or if not try to prone him again.
I also have Green Flame Blade through magic initiate and once I have a guy downed and grappled I drag him around to other combatants and use GFB to land extra GFB damage. He either attacks everyone at disadvantage or wastes an entire action to break the grapple (at which point I will do it again).
Add in using a spear for Sap and stunning strike or using patient defense and combine one of those with deflect attacks and the character is extremely effective at defense as well.
There is so much flexibility in this build and the character is pretty good at skills as well out of combat. What is described above is 6th level (Monk 5/Rogue 1). The PC is currently level 12 (Monk 5/Roge 7) and I am doing 4d6 on sneak and also I can throw a Cunning Strike on there to poison or trip the enemy.
I use daggers and a spear in my build, but I think it would work even better with a staff, opening up with an attack that can topple and then grappling when the guy is already down.
I also have the Jump spell on Magic Initiate which gets crazy with my awesome movement and slow fall. I use it to jump over a Wall of Fire or a Blade Barrier and get to the casters on the other side and then drag them through their own spell and I have evasion while grappling (they usually drop concentration). Our casters throw these same spells and I do drag the bad guys through them and jump back and forth from one side of the wall to the other. This is only 1 combat a day though since I can only cast Jump once.