Abusing D&D 5th edition

There was a bit of debate about what to play after my gaming group finished The Lost Mines of Fandelver (or whatever it's called) a couple of weeks ago. One guy wanted to play Burning Wheel, but refused to play GURPS. I would have preferred to continue the Rise and Fall of Hydra or start some GURPS game, but I wasn't prepared for the first and there was too much resistance for the second. More or less by default, we ended up playing D&D 5e with the "Princes of the Apocalypse" adventure and new characters.

Lucky Rolls and What To Do

Our GM, +Will Scott, said we could roll for attributes, and I got unreasonably lucky: 17, 17, 16, 16, 14, and 14 (+Theodore Briggs can bear witness). We were already going for a party that could see in the dark, so ended up as a half-elf cleric with STR, WIS, and CHA of 18, CON of 16, and DEX and INT of 14 (my poor dump stats!).

In dividing the party rolls, my cleric ended up being the tank, the healbot, and the perception guy. Half-elves with WIS 18 can start with proficiency in Perception, so I have a +6 Perception and feel reasonably good about my chances of noticing stuff. Clerics are healbots, especially if they take the Life domain, but I had just finished playing the example dwarven Life cleric and wasn't really impressed with the domain and didn't feel I needed the extra juice, especially with a bard already in the party for backup healing (and potentially a druid coming from our 5th player).

The three domains that provide a cleric with heavy armor proficiency are Life, Tempest, and War. Between War and Tempest, the trade-off is a retributive attack versus a bonus action attack and slightly different domain spells. I went with Tempest for the retribution attack and the ability to cast Thunderwave, expecting that would synergize well with the wizard's Thunderwave and the bard's Thunderwave.

The Limitations of Tankiness

With Chain Mail armor and a Shield, my character is starting with a respectable AC 18 that will only go up as I improve to Splint and Plate armor and get magical enhancements. With a good AC, decent HPs, the retributive thunder strike, and Thunderwave, I feel pretty positive about my ability to wander into a mob of foes and come out on top. What I don't feel as good about is my ability to hold a mob's attention.

The problem is that my defenses are too good: monster attacks are less likely to hit me, and any monster that successfully hits me takes 4-9 points of damage. The rest of the party has AC 14 or so, less HP, and no retributive strikes, so it makes sense for monsters to attack everyone else instead. I only get 1 opportunity attack each turn, so I don't think I'm going to be very sticky. Since a large part of the tank role is to encourage monsters to attack me (since I can take their hits) instead of the squishy wizard (who can't), the lack of stickiness is a problem.

The Sentinel feat looks like the perfect solution to the problem, but I wouldn't get it until 4th level at the earliest. Based on my experience with Lost Mines, that means I'd have it for 1-2 play sessions before the end of the game. That's really unsatisfying.

I think I'm going to ask Will if I can sell of the half-elf +2 bonus to Charisma for a feat. In theory, this should be a fair swap, and it's not like my character is going to feel inadequately social with only CHA 16. If I can't do that, I'll have to try some clever positioning, I guess.

Does anyone else have good suggestions for how to turn a half-elf cleric into a good defensive tank?

Update
You can read about the adventures of this character, Caius Flavius, and his elven compatriots under the Princes of the Apocalypse tag. Will let me swap +2 to Charisma for the Sentinel feat, and Caius has proved to be admirably sticky and good at damaging foes who are foolish enough to not attack him, or to attack him, as they chose.