You will lack knowledges as you say, and only a wizard can fix it properly while being a great fit in your team but you said that you would rather no play one. If you wish to play one though, diviners make the best allrounders and abjurers make very durable ones if you can cheese the ward, either by being a gnome with snifervin magic, having the alarm spell or dipping two lvls of warlock. Bladesingers are the best at keeping concentration and have the highest AC if this is your cup of tea.
You also said that you may want to avoid bard, but life cleric 1 / lore bard x makes for a great armored healer (probably the best from 7th lvl and onwards thanks to goodberry) while retaining all the awesomeness of the bard, who is just so much better compared to the bard of previous editions (without a ton of splatbooks at least). Definately much better than a pure life cleric.
Knowledge cleric is subpar as a main class, although it makes for a great dip for a wizard.
All the other suggestions that have been done are also good fits for your group for the reasons that have been mentioned. Basically, the damage and tanking part have been covered and you can amplify the efficiency of your group by supporting them, be it controlling the battlefield, buffing them or healing them. If you can also provide good dpr in the same time good for you, but it is not necessary.