98IV Tyranitar ... with Bite/Fire Blast, power up?

I wouldn't. But I actually caught one like that wild @2500, and while I won't power it up, it's actually been pretty good against Blisseys. Go try it out

It depends on many factors.
How many candy/dust do you have?
What level is it right now? What level are you?
What is the gym situation in your area? Lot of stagnant gyms?

It is definitely a bad moveset for both attacking and defending. However, if the gyms in your area are stagnant, moveset doesnt matter as much and CP is everything that counts.

I think it would be worth to power if up if:
1- gyms in your area are stagnant and on your team
2- you have enough candy/dust to get it to a decent CP where you can stay in those gyms without getting cycled.

There's at least a couple of month before the "gym overhaul" u'll be able to collect hundreds of pokecoin from that tyranitar by then, which in my opinion, is worth it.

Just don't touch him for a moment... His base stat is awesome but the moves is not that good enough...

i wouldn't, larvitar candy is just too rare to spend on a sub sub suboptimal moveset.

Why not?

Only a 100% Tyranitar can stand on top of your beast. I have one with IronTail/FireBlast 98%IV too and I power him up all the way.

i'd power it up to at least level 30. i mean why not, right? it's still a freakin tyranitar with almost 100% iv. it's just like having a dragonite with dragon breath and hyper beam.

Bite/Fire Blast is a good move set for Arcanine, and I've taken out a ~2200CP Blissey with an Arcanine. So, my guess is the move set is ok, but not spectacular. I also think it will work ok without powering up. So, I'd save my candy to make another one, with maybe a better move set.

Since I catch a Larvitar almost every day, I'd definitely power it up. If they are as rare as Chanseys in your biome I'd wait.

At level 30 it would take a top 5 spot in almost every gym in my city, and well above the Blisseys. He will bring you a lot of coin and dust if you power him up.