It's definitely annoying to see but absolutely what I'd expect in a real situation.

1: These aren't the main heavily armed force in the future timeline who have a better grasp of the situation, it's QA. Their remit and tactics are probably meant to contain small incidents, not to take on an entire host rebellion which most probably aren't even aware of. As such there is also no reason why they would keep helicopters and tanks on site and why they underestimate the hosts' abilities.

2: Early on they have a specific goal, to obtain Abernathy, they can't risk outright destruction without securing that objective first. Also, as we've seen hosts have been rounding up investors/board members. Without knowing who is inside the compound I doubt they want to risk accidentally blowing up real people.

3: Even if Delos did keep assets like tanks and helicopters off site I still wouldn't see them being deployed so quickly as a first resort. Those things aren't cheap to deploy. Good luck trying to argue with the board-members to sign off on deploying costly equipment to destroy their biggest source of income. Also deploying helicopters/tanks or other armed assets onto Chinese territory is going to raise eyebrows which it appears it did later in the timeline when we see the Chinese Navy involved who Delos are pushing back help. Expensive equipment and bureaucracy; two things that don't gel well with people whose main goal are quarterly profits.