There's basically three approaches to take with a team using Arbiter:

1. Do a double-boost into a nuke finish. Often this is done by using someone like Deacon. Typically, the third in line is a debuffer like Serris, and then you end with a big AoE nuke. You need to tune the entire team to avoid cut-ins. Use a calc like this to ensure that happens: https://deadwoodjedi.com/arena-calculator/
2. Boost into a provoker. This is my personal strategy - I run Arbiter and boost into Maulie. Again, typically the third in line is a debuffer. Personally I use Lydia. Then you have your big AoE nuke.
3. Boost into a CC'er. I used to run this one - Arbiter into Kymar for an AoE sleep, then Serris and then a nuke. I stopped running this mainly because it was hard to get enough accuracy on Kymar to reliably land the sleep, and also still be fast enough to prevent cut-in, ontop of being vulnerable to affinity weaknesses.

I will caution you though, that 300 speed is really not enough. The lower bound on most speed nuke teams is up to around 335 now. Anything less and you'll likely lose against those other Arbiter teams. 

Thanks, Kram. 

I'm sure I'll get more speed on her with time, but right now it's the best I have. 

For a double boost, I could use the usual suspects (Seeker, Gorgorab, Dazdurk). I may also incorporate Doomscreech or Tarshon for Def.up for the occasions when I use Ragash as a debuffer/mini-nuke.

For provoker, I could use Krisk since his A3 also increases speed for allies and he comes with shields. Also, I maxed GH bonus for Void Accuracy on my way to Arbiter, so that works out. 

For CC, I can use Psylar in Stun. Can't rely on Stun much due to the low percentage, but even 1 out of 4 stunned can throw off their tune. Plus, she really slows the team down.

I think Krisk may be the best bet for me then, huh? He's in my CB team, so I'll be keeping him fast anyways.

Arb-Krisk-[Debuffer]-[Nuke] is a very viable team. Just make sure Krisk is fast enough to go after Arb with no cut-in, and is running ~350-400 ACC.

It'll take some gearing, but at least there is a direction. Thanks, Kram. 

kramasky  pretty much covered it, both approaches have up and downsides

If you go with arbiter into provoker or crowd control you have the gear challenge of being quick enough but also having sufficient accuracy to reliably control

If you use a double turn meter, expect to be ruthlessly farmed by everyone with tormin, its a free kill to them and you have to tune it properly.

Gratz on arbiter by the way! 

Did some Dragon farming and reset the masteries. 

Got my Krisk to:

49K HP

5100 DEF

252 SPD (which is within 30% of Arbiter's 302 SPD)

353 ACC

I think I can get my Arbiter up to 327 SPD and not have to worry about Krisk lagging behind. I don't need to beat Platinum, just need a team strong enough to farm up Great Hall in Gold 4-5.

I highly recommend you use the above-linked calculator to tune properly. The worst thing is when you think you're set, and then discover you were off by a few points and get cut in.

Though as an aside - you don't need a "strong" team for G4/G5. Just farm the solo teams.

I find less and less solo teams nowadays, so I have to resort to raiding an Arbiter team here and there. 

I think my Snuke team is working well together: Arbiter - Krisk - Ragash - Konstantin. I'll build a couple other variations with Madame Serris and Genbo for specific scenarios.