Because casters can only maintain one Concentration spell at a time, can only ever cast one spell per round (in most circumstances), and most duration spells can be nullified by forcing Concentration checks, debuffs are actually not super strong in 5e. Players use them more often than enemies do.
Additionally, Saving Throws are generally divided into two groups: Important and Non-important.
Important:
Dexterity
Constitution
Wisdom
Non-Important:
Strength
Intelligence
Charisma
You'll note that every single character starts with proficiency in one from each of those lists. Dumping one of the non-important stats won't be a big deal, and dumping stats in general won't cripple a character. Barbarians kinda need Wisdom, because Hold Person is a good resource that will nullify their Rage, but that's about the extent of "needing" saving throws goes.
I wouldn't recommend multiclassing casters, unless you're aiming for an explicit feature that ties in to your concept. With the Life Cleric/Sorcerer build, it's about getting your Twinned Spell and Distant Spell Metamagics to use with Warding Bond and Revivify.
An Arcana Cleric is perfect as its own "Cleric+Wizard" hybrid, as it does everything you want from a wizard (Blasting + non-combat utility effects), with the support and armor you'd expect from being a Cleric. A straight Arcana Cleric would do well for the team.
As for building an Arcana Cleric, it's really quite simple: Get Shocking Grasp, Firebolt, and some non-combat Wizard cantrip (Mage Hand?) for your starting Wizard cantrips. Try to diversify your selection, so that your cantrips aren't solving the same problems (so don't get both Firebolt and Ray of Frost). You'll only ever really need one melee cantrip and maybe 2 ranged cantrips for combat.
After that...go nuts. Most healing can be solved with Healing Word and good use of Hit Dice during a Short Rest, so just try to make sure people don't die. At level 6, you'll be able to dispel magic from your allies, so just keep that in mind. Healing Word is a Bonus Action spell, so you'll still be able to cast a cantrip or make an attack after using it. Arcana Clerics are hard to build incorrectly.
One particularly fun thing you can do is take a level into Fighter and get the Spell Sniper feat. With it, you can cast the weapon-attacking SCAG cantrips with a reach weapon (like a whip), being able to hit an enemy with a spell like Booming Blade from 10 feet away, enough to hit and run your targets.