Yeah, this is how we played it in 4e ... but all of that defensibility came from the runepriest. Gave out bonuses to defenses regularly either directly to PCs or in a sustainable area, provided always-on resists to every ally in aura 1, etc. Or if there weren't many combatants would give penalties to foe attacks. Also gave out buffs to allies to finish combats faster. Common encounter powers would do things like give a penalty to attacks equal to Wis (+6) + number of adjacent allies to a foe as an effect (plus do damage on hit), or close burst 5 give all allies +5 to all defenses and all enemies hit -5 to all defenses until end of turn (that was from a paragon path). Even at-wills can do things like have out -2 to hit foe defenses and +6 (Wis) AC to the next ally to hit it.
In other words, taking care of everything you just said, but without the other characters having to do anything, is what the runepriest is trying to emulate with a 5e character.
In 5e, as a cleric, this might look like..
- Bonuses to Defenses: Resistance or Bless ups saving throws, Shield of Faith ups AC. You'll have to choose between them since they're both concentration, so it pays to know your enemy - breath weapons and spells mean Bless or Resistance, while ogres and archers probably means Shield of Faith.
- Damage Reduction: Warding Bond and Protection from Energy work well here. Again, it'll pay off to know your enemy - you can't just blanket everybody.
- Penalties to the Enemy: Bane is the most obvious, but action-denial is actually super effective there, which means Command has a good role to play.
There are two big re-calibrations you might need to make.
First, that there are less "fiddly bits." 5e doesn't have a lot of options for giving -2 or -5 penalties to things - don't look for large modifiers (or multiple small modifiers that add up to something big). Instead, look for advantage, disadvantage, range, terrain features such as cover, and resistance (which is half damage from some kind of attack). From a character construction perspective, once you have one way to bestow resistance, advantage, or disadvantage on a particular check, especially at range, you've "filled" that slot, and now do all you need to do to help your party in that capacity. This isn't hard to do, and you're not going to get an abundance of options that do less than that. Once you can give an enemy disadvantage on attacks (or deprive them of actions), you don't need to worry about hindering their attack any more than that. Once you can give an ally advantage on a saving throw, you don't need to worry about buffing their saves any more than that. Do it once, and check it off your list.
Second, you won't be doing it to the whole party all at once, at least at low levels. Use
shield of faith on the character with the highest AC and most HP, and have everyone else stand back and plink away at range, and you'll be set for a fight with a big critter. A fight with an army of little critters is going to need choke-points and good control magic to quell. But don't worry if your squishies need to take a hit or two - they can.
The party also had a paladin, but took one of the other options besides lay-on-hands. Others were an elven ranger (archer), a essentials thief and a vestige pact warlock multiclassed into barbarian. Not a lot of healing elsewhere.
This won't be too dramatically different in 5e (except that paladin healing is really useful thanks to the lower amount of HP, and rangers can pick up healing magic, too). Keep your range as an elven ranger, your thief might want to consider the extra safety from a bow (sneak attack works at range!), your warlock/barbarian will want to be blasting from a distance, or using darkness/invisibility to close. Your party might also consider setting up ambushes and might find a big, open area with the paladin or the warlock or the priest designated as a "puller" who can grab the attention of a group of gobbies and provoke them into a chase (recommend a high Charisma for that - persuasion and intimidation and deception can all be good for luring enemies into doing something foolish).
Combat things on your terms, and think strategically, not just tactically. Ranger/Warlock/Rogue have good stealth skills - put 'em to use in avoiding combats and getting surprise!