The reason bots only select a limited set of heroes is because the AI hasn't been scripted for every hero in the game yet. Assuming you pick before them, the bots will then try to counterpick any heroes you or your allies have.
You can also 'suggest' heroes which will cause allied bots to choose those heroes, if AI exists for them.
As far as I can tell, the only AI scripted heroes currently are:
- Axe
- Bane
- Bloodseeker
- Bounty Hunter
- Bristleback
- Chaos Knight
- Crystal Maiden
- Dazzle
- Death Prophet
- Dragon Knight
- Drow
- Earthshaker
- Jakiro
- Juggernaut
- Kunkka
- Lich
- Lina
- Lion
- Luna
- Necrophos
- Omniknight
- Oracle
- Pudge
- Razor
- Riki
- Sand King
- Shadow Fiend
- Skywrath Mage
- Sniper
- Sven
- Tidehunter
- Tiny
- Vengeful Spirit
- Viper
- Warlock
- Windranger
- Witch Doctor
- Wraith King
- Zeus
Valve periodically adds new bots in their weekly updates, but as of late they have been focusing primarily on AI enhancements instead of adding more heroes.
Well if you are really affraid of being hooked versus Pudge, having wards high ground is the best solution.
You can ask your support to put up wards so you will always see where pudge is (see screenshot at the end).
Then as an Invoker you can put an early point in wex just fot ghost walking away. This might delay your dual forge spirit (in the QE built) but if you really feel insecure that might be the best way to go.
With any mid hero you have to not make the basic mistake versus pudge which is : try to escape the rot by running. If you ever get hooked, trade hit with pudge and burst him with your spell. If you try to run you're almost certainly dead. Pudge has a really low armor at low level so your right click damage will hurt him badly, plus remember that the rot inflict damage to himself too so you can often turn a hook into a kill for yourself, just dont be afraid to manfight him. Pudge players tend to get overconfident when they land a hook, prove them they should not.
Another great tip is : rot does not dispell healing salve until its level 4, so you can use a salve to get some hp back between 2 hit and that might save your life.
Screenshots
Those wards' position can be used to avoid any kind of early ganks. You can watch the minimap to have an idea on what vision it gives.
When you are on the Radiant side :
When you are on the Dire side :
This last observer is usefull to scout mid highgrounds at all time to avoid hooks (you can place it on both side but preferably the enemy's side) :
Best Answer
Several items or skills in the game reveal invisible units. Here is a list and few tips on how to counter the problem :
Items
Skills
Extra Information
Always be aware that the enemy team will sooner or later get a way to detect you. By checking regularly the enemy's heroes inventories and looking for detection items, you can avoid a lot of unfortunate deaths.