Q about evolving some good pokemons

For me your Dratini is your best choice, it has almost perfect ivs and Dragonite is excellent on both attack and defending, just look for the DT/ O or H movesets

If that 97.8 IV T-tar has good moveset I would power up him to the level 30 and evolved Dratini.

Those are best choices in my opinion.

aim for two Tyranitar (max out), two Dragonite (max out), Blissey/Snorlax (go with ~lvl 33 for now).
Under the condition that you have none of them:
power up all of them with best moveset, for Dragonite go for one DT/O and one DT/Hu, Tyranitar go for one B/SE and B/C. Snorlax ZH/BS and Blissey ZH/DG (two in total, so either Snorlax and Blissey or two Snorlax/Blissey.

If you are very active in the daily gym battles, #6 Blissey is a top priority.

If your primary focus is boss raids, #3 Tyranitar is a great choice.

Hold on Dragonite, as the Japan Yokohama event hinted that Dragonite will be a raid boss in the expected, next boss rotation.

Thank you for producing a well thought out question with good information... It's rare on this site. How you should proceed is dependant on your area. You are obviously intelligent enough to make the decision on your own as long as you realize defenders are not quite so important as they once were.