I may just be impatient but I feel as though my branch mine should be getting way more diamonds than it is. My main branch mine hall goes back 70 blocks with 2 tall sub-halls that go back another 10 blocks on each side. All of that and I've mined a total of 5 diamond ore. Am I doing something wrong?
Well, most of the effort you put into the main hall is wasted as far as obtaining diamonds but if you like the look then go for it.
For maximum results you should be at least a block lower, at Y=11 you are exposing layers 11, 12, 13 and 14, layer 14 has about half the diamonds as layers 5-12 (layer 13 is only slightly less than 5-12 so that doesn't matter much).
Your branches are at least a block too close, most diamond veins are 2 blocks wide and so can't hide in a 3 block thick wall.
TheMasterCaver, who really lives up to his name, is always pushing for 6 blocks between tunnels as even better than 3, that's because if you mine the other ores that sometimes exposes diamond veins.
Personally I'm sticking to 3 blocks between tunnels because I do a LOT of mining and spreading the tunnels out would increase the length of the main tunnels.
Otherwise ore veins are kind of "clumpy", sometimes you can dig hundreds of blocks finding nothing and then you find 3 real close to each other, so don't give up.
From my standpoint you've hardly started, once I get enchanted diamond picks my branch tunnels can be up to 500 blocks long, so your branches are about equal to one or two of mine and some tunnels I find diamonds in, some I don't.
As the previous poster indicated, your design is not efficient and you should follow the advice given. Also if you are simply going for efficiency and don’t care how it looks you don’t need to waste time and effort making a huge grand central corridor. A simple one-block wide corridor will do. In that case it can be helpful for orientation purposes to lay a piece of carpet in the main corridor where it branches off. Hopefully you are using a pickaxe enchanted with Fortune. If not, uncover any diamonds you find but don’t mine them until you have the enchantment. I did that for the first time in my 1.15 game and for the first time I’m swimming in diamonds.
I may just be impatient but I feel as though my branch mine should be getting way more diamonds than it is. My main branch mine hall goes back 70 blocks with 2 tall sub-halls that go back another 10 blocks on each side. All of that and I've mined a total of 5 diamond ore. Am I doing something wrong?
Well, most of the effort you put into the main hall is wasted as far as obtaining diamonds but if you like the look then go for it.
For maximum results you should be at least a block lower, at Y=11 you are exposing layers 11, 12, 13 and 14, layer 14 has about half the diamonds as layers 5-12 (layer 13 is only slightly less than 5-12 so that doesn't matter much).
https://minecraft.gamepedia.com/File:Diamond_D_28x.jpg
Your branches are at least a block too close, most diamond veins are 2 blocks wide and so can't hide in a 3 block thick wall.
TheMasterCaver, who really lives up to his name, is always pushing for 6 blocks between tunnels as even better than 3, that's because if you mine the other ores that sometimes exposes diamond veins.
Personally I'm sticking to 3 blocks between tunnels because I do a LOT of mining and spreading the tunnels out would increase the length of the main tunnels.
Otherwise ore veins are kind of "clumpy", sometimes you can dig hundreds of blocks finding nothing and then you find 3 real close to each other, so don't give up.
From my standpoint you've hardly started, once I get enchanted diamond picks my branch tunnels can be up to 500 blocks long, so your branches are about equal to one or two of mine and some tunnels I find diamonds in, some I don't.
Just testing.
As the previous poster indicated, your design is not efficient and you should follow the advice given. Also if you are simply going for efficiency and don’t care how it looks you don’t need to waste time and effort making a huge grand central corridor. A simple one-block wide corridor will do. In that case it can be helpful for orientation purposes to lay a piece of carpet in the main corridor where it branches off. Hopefully you are using a pickaxe enchanted with Fortune. If not, uncover any diamonds you find but don’t mine them until you have the enchantment. I did that for the first time in my 1.15 game and for the first time I’m swimming in diamonds.