I definitely disagree and think it is a major plot hole since Drogon was TOTALLY surrounded over the bay AND there were a plethora of other ones along the walls. They had a sweeping overhead shot depicting how many ships were there and there were hella angles to be used even if not straight up. It was wack. Not to mention D&D saying we basically saw the end of the Dothraki in Winterfell and then somehow TONS of them were available to fight. The Golden Company was supposed to be 200,000 strong and they definitely didn't look that big (though I'll be fair and assume some were offscreen). The inconsistencies between what they say and do just are baffling.
I totally agree that there were some elements of foreshadowing. But honestly way too subtle. This season they bash you over the head with it ex "Hey guys have I mentioned how safe the Winterfell crypts are? They're like the safest of safe". Even still, some examples make zero sense. Beinoff recalled Dany not having sympathy for her brother dying as foreshadowing.....the guy tried to sell her into sex slavery and then tried to kill her! Even the Tarly's. What was she supposed to do? Get talked down to by her first prisoners? No. Prior to that, she only went after slavers. And the whole time recently she was listening to her Advisors...Jorah. Tyrion, and Varys. She even went North to fight a war to save other people! If they took more time to actually show her going mad that would be one thing but it felt like she basically snapped in an episode due to how they had her respond to other scenes (Jon revealing his secret).
Haven't considered the bolded part. Good point. But still, I think that just means invest more time and energy. They had virtually limitless resources. Lots of characters are acting differently than their normal selves, and if you want the twists and changes to be believable, you set them up. Look no further than earlier seasons.