Dualaity between Leona and Diana.
I suppose the my biggest gripe with the lore changes is the fact that both Leona and Diana were forged under very similar circumstance, but chose effectively different paths as a result of their personalities and the support that had received.
In Leona's old lore she was referred to as a problem child due to her unwillingness to adhere to her people's traditions. She was to be executed for this very view. She was saved due to the power of the sun.
In Diana's old lore she was also referred to as a problem child due to her willingness to question her people's traditions. She was to be executed for this very view. She was saved due the power of the moon.
But unlike Leona, who had a benefactor in the Solari. Diana was effectively alone. Now, to me, the new lore loses the duality that was presented by the old lore. Leona is no longer a problem child who would consistently go against tradition, but instead a zealot, who had effectively a 1 time lapse in judgement.
I am not sure, but to me, the core of her character is no longer there.