I know I am not even close to the only one who is bothered by this. Almost every single person who saw the field of fire battle (which was epically awesome by the way) is thinking it, so I'll go ahead and say it.

Dany knows that the Lannister army just took Highgarden, and probably sacked it and will be carrying the loot from the castle to King's Landing. Firstly it bothers me that all the gold waggons are safely inside KL, while the rest of the army has not yet moved anywhere close to the city. I understand why the plot needed the gold to reach KL and be paid to the Iron Bank, so whatever, I won't waste breath over it, though I really really want to.

More to the point, Dany's forces arrive at the flank of the Lannister column, with incredible lack of sound discipline, losing all element of surprise, and yeilding the advantage that the flank position would have given them. Lannisters form line, and prepare to receive cavalry. Dany flying overhead in air support, with a unique birds eye view perspective of spears and shields in line, and a column of wagons stretched out on the road. This is where my trouble begins.

Cavalry, even the fiercest one, has very limited effectiveness against a shield wall supported with pikes and/or spears. Sure Drogon punches a hole in the line, and even without the hole, through sheer numbers, the Dothraki would have overcome the line. Though many Dothraki lives were lost in the process, as the melee ensued, while Dany engaged in repeated strafing runs of the wagons. WHY, DANY, WHY?!! You know what is really really effective against a column of wagons stretched out on a road while their escort is taken away to form up in battle lines? Cavalry! Russian Cossacks starved French soldiers by reapeatedly ambushing any supply column that was not adequately protected, while avoiding any engagement with French cavalry to preserve their numbers. Dany's strafing runs would have been far more effective against the soldiers conveniently lined up to form up the shield wall instead, while the Dothraki went and commandeered the wagons.

Instead, Dothraki engaged in a melee fight, losing men and horses crucially required for the fight at KL, while Dany flies around blowing up wagons, which she'd have known with any amount of thinking contains the loot from Highgarden, probably vital food stores that can be diverted to the Unsullied.

Instead, if Drogon had engaged the shield wall, and Dothraki had swarmed the wagons, her casualties would have been very minimal, and she'd have captured a lot of useful stores from the wagons. Also, Bronn wouldn't have been able to deploy the Scorpion.

I conclude that in the interest of theatrics, kick ass battle scene effects, valiant fighting (Jaime is slaying Dothraki left and right using his left hand...), D&D utterly screwed any tactical or strategic acuity on the part of Dany.