So... liek uh?... On 1.7.10 its a pain in the rear to mine blocks, they always seem to re-spawn I mine blocks and like 85% of the blocks re-spawn, is this a server thing or just me? On 1.8 the blocks work just fine but it is laggy as crap for me on 1.8.
I'm forced to play on 1.7.10 because 1.8+ makes my computer lag to much, like you. This only happens to me when I'm sprinting, and about half the blocks re-appear. It happens mainly when you do it in a straight line, spamming the shovel. It will be a pain, but either don't sprint as much, or don't spam as much.
Uh.. You see, that's a problem for me xD I have played spleef for about 2 years, and I have developed a habit of rapidly mining and doing circles, well.... I used to.... I'm not so good now xD
Everybody has this. Some blocks just respawn for no reason, but 85% is a lot o.O I would say that 5 to 10% of my deleted blocks respawn. You could try 1.8 and put your settings in a way that it doesn't lagg too much, or either play in 1.7.10 and follow what @Tevvet said.
I don't think whether you use 1.7 or 1.8 should make a difference. Perhaps try installing OptiFine to reduce lag. I have also tweaked our anti-cheat settings a little more, which may help.