Kramaswamy is over exaggerating the situation.
You don't need High Khatun with 280 Speed to get into Silver Arena.
A 280 Speed hero is like a Gold 3 or Low Gold 4 hero.
High Khatun with a minimum of 200 Speed is more than enough to get into Silver 1 Arena.
High Khatun with a minimum of 250 Speed is more than enough to get into Gold 1 Arena.
If you really want to use High Khatun, The Arena set up you should build is a Speed Nuking Set up.
Leader: High Khatun - 19% Speed Aura
1st move: High Khatun ----> Turn Meter Fill + Increase Speed
2nd move: Seeker ---------> Turn Meter Fill + Increase Attack
3rd move: ??? --------------> AOE Def Down Hero
4th move: Astralon --------> AOE Nuker
The only hero you are lacking from your roster is an AOE Def Down hero.
The good news is you can get a F2P AOE Def Down Hero in Chapter 9 Campaign (Warmaiden)
You can use Warmaiden if you don't have anyone esle.
Alternatively, you could make a Defense team.
I'm not sure whether or not you want to make one.
I guess it just depends on what you want really.