Arcanine Solo Failed
Fire Fang Fire Blast. Tried four times and getting closer each time but still could not make it. Lineup based on Pokebattler simulation. In my last trial, lineup is:
WGHP Vaporeon; RTSE Golem; BSE Tyranitar; CDP Machamp; DCDB Dragonite and (did not use) DCH Dragonite (ADS and level shown in the pokemon name). Did not dodge.
Thinking whether i should use BHP Gyarados (CP 3001) as my fifth Pokemon. Or I should power up another Ttar to 30+ level (all my other Ttars are at level 20 from raid)?

Answers
Time to win is too slow for all except Vap and Golem. You need more of those. Until Arcanine has Wild Charge, then Vap is gone.
Haven’t done any Arcanine solo yet, hesitant to power up another couple of Golems needed since I’m not interested in Arcanine. From what I understand Arcanine is like Vaporeon in raids, DPS is everything, so no use in bringing secondary pokémons to the battle.
Whiteout Wild Charge, Vaporeon x 6 is da shit, and otherwise Golem x 6.
The difficulty here is that both Bite and Water gun suck as fast moves. So if you are caught with a lot of health left but not enough to get another charge move off then you are slowly killing your DPS as well.
Since you need to average just over 17 HP per second the best time to die is obviously right after a charge move. However, since B and WG suck so much your ~20 HP/S damage rate (more than enough) can drop all the way to ~15 HP/S (not fast enough) depending on how long you go before dying.
I've seen some videos where people manually switch to the next mon rather than waste all that time with useless fast moves. I haven't tried it yet, but I imagine if the decision was made at the right time it could save a bunch of time. The down side to this method is if your next mon dies, it will automatically switch back to the one you just swapped out.
For this reason I like to lead with RT/SE golem since the fast move is good even if you don't get the second SE off. Also I noticed that nearly all your options are 1 bar charge moves so you might want your 5th mon to switch in a multi-bar charge move option (such as your Machamp or a DT/O dragon).