Just wanted to share my deckbuild that I'm currently using.

Here are my stats of the last 2 days playing causual with default control rule set.

Klick to enlarge.

Here is the build:
druid mech deck

Feel free to replace any card you don't like or have.
Savage Roar is not always played correctly and can be swaped out.
Some card draw like Nourish would be a great replacement.

My main account is still banned for using Hearth Crawler, so I don't have many cards to test different builds and the following is pure theory.
All the GvG cards in this deck are from ~15 arena runs and I wouldn't craft any of them.
Just add some strong druid removal and browse your collection for mechs.

Remove:
1x Savage Roar
1x Innrevate (good at the start, but often a dead card)
1x Mark of the Wild

Add:
- carddraw: Nourish, Ancient of Lore, Jeeves (don't know if this is a drawback because you'll have some spare parts in your hand)
- sticky minions: Harvest Golem, Arcane Nullifier (real pain for hunter), Piloted Shredder, Mechanical Yeti
- buffs: Enhance-o Mechano
- silence: Keeper of the Grove, Ironbeak Owl, Spellbreaker
- stronger endgame: rag or whatever

Specific rules should help a lot.
The bot often keeps weird cards in starting hand (like swipe) and doesn't realy know what he's looking for.

Reduce bot A.I. parameters to 20000, 100 may make it work better.

If your computer is slow, set it to 10000, 0.