I don’t think there is a difference in drop rates depending on player level.
That would need some labor to programm without any direct payout for TacticSoft.
If there was to be different drop rates then it would certainly depend on real money investment of a player.
A player buys that offer of 795 tokens for 10 bucks that sometimes appears and then purchases 3 discounted premium packs for 3 * 234 = 702 tokens.
If he gets a high legendary drop rate from the packs then he would have the feeling of success and would be more willing to spend money on the game again.
So increasing the drop rate of legenday items depending on how much real money a player has invested into the game (and therefore into TacticSoft’s pockets) would have a direct influence on the future investments of that player and therefore on TacticSoft’s earnings from that player.
Hence if they would go to the trouble of different drop rates for legendaries then they certainly would go for rates depending on the investments from players.