You don't lose battles on power difference, you lose them because you're not fast enough, or your team doesn't have good synergies, or is badly geared, or whatever. I just won a battle with a similar power difference, me around 95k vs opponent at 160k. And he didn't even have bad champions - HK, Elhain, Sinesha, Apothecary. All good in arena, but as a team, lacking in synergies, buffing and debuffing. 

Keep in mind the great hall bonuses. Right now, you are getting an additional 5 acc. When you have it at level 10, the bonus is 80 acc. That's significant. So your great hall will help quite a bit as you level it. 

I don't think they discredit power in so much as they say that it's not necessarily an indicator of whether you will win or lose. There's more to it than just the number. If I recall correctly, resistance will inflate the power number more than hp or  whatever. As L9753 said, synergies play a part. Tuning your champions to go in correct order plays a part. 

You gear will be improved over time. You are using a common 4* ring for example. As you get 5-6* higher quality gear, with the correct stats on them, you will hit harder, hit faster, and win more. 

While you should be playing arena, which you are, in order to build your great hall bonuses, you also need to farm the dungeons that contain the gear you need. For example, you don't have an amulet yet do have a banner and ring. So get back in spider and get an amulet. Equip something in a bare spot. Break set bonuses if the pieces you use are worth it. Play faction wars and use the drops to increase your stats on the artifacts.

Speed is king - Most gold4 players have 300+ speed Arbiters/Kymars/Dutchess/Shazzars that also have the best Speed Auras in the game.

When your damage dealers are geared really well they can tear apart most teams as long as they go first.  On your Gorgorab you should literally focus on only speed and no other stat, equip him with as many double and triple speed stat rolls as you can, and he should probably only be wearing speed set pieces.

Also, don't forget about finishing masteries. 

If you ask me about the comp you're running though, I'd use Madame Serris instead of Athel. This will make the team more well rounded.

Get as much speed as you can on Gorgorab, stack crit rate and crit damage on Skullcrown, get tons of Accuracy for Serris, and that should get you to Gold 4. 

Some time ago i had nearly a team like u and it was no problem for me to come close to platinum.

Important is speed speed speed

u need dutchess as lead ( i had 280 speed some months ago)  then i used apothecary ...nearly the same speed 

u have scullcrown, sinesha, madame...really good options...should be no problem for u to reach  higheer lvls.

And dont look on player power...... i had 150 k player power a time ago and i was in platinum...(nearly all others had over 200k)but my arbiter has 330 speed...to be the first is much important with a squishy not much resi team

My Problem like many others have is that i dont skilled most of my arena champs purely on arena, because i use some of them in clanboss or dungeons too

Good luck for u!

Thanks all that's really helpful, I think it's what I had been mostly thinking but hearing it from others is reassuring and there's lots of good tips in there too.

As some have said I've been stuck between building champions for area or for other content and ended up with a mix that doesn't really work for either.

Madamme is a new pull so trying to gear / level her up now along the lines suggested but it's also become apparent my champions that I thought were geared ok have a couple of now obvious deficiencies. E.g. skullcrown and sinesha have loads of crit damage but <50% crit rate so not overly reliable - I think I must have built them when I was newer and never really went back in detail.

So back to farming gold and gear now - at least I think you've given me a plan so thanks again!

If you want fast nuking I recommend the following team

1. Skullcrown (leader for speed aura) (build her with attack, crit dmg, crit rate and enough speed so the enemy dont go before her)

2. Gorgorab (speed all the way)

3. Apothecary (speed all the way)

4. Madame serris (enough speed)

The speed order should be: Apothecary, gorgorab, madame serris, skullcrown.

Skullcrown should nuke the enemy team down.