Why can you get dived at level 5 and have nobody die to the tower? The towers in this map can literally be ignored by any tanky character; we just got dived by a Karma / Garen / Jax at level three. None of them died.

lol i dived as hec at lvl 4 and killed a yi

How about you simply change your mentality.
towers are safe zone > towers need to be protected

Why am I defending something which is useless to me?

Ignored by any tanky character? I was pushing top with Teemo and 2 of the enemies came up from behind, so I ran into their base.

Through the lane turret
Through the base turret
Behind their nexus
Through their bottom base turret
Then into the jungle with 200 HP to spare

The only thing "tanky" about my build was a Blackfire Torch.

I agree wholeheartedly! The towers are too weak and the spider's too strong. My team went for spider at level 18 (Katarina had a full build, I was close [as Garen] and our Elise was close to a full build as well) I had about 3.7k health with 150+ armor and it got me to less than half from full. Elise and Kat almost died from it (having gone in with full hp.) and their team came after we had killed it and killed us all easily (Amumu ult) despite the fact that we had maintained team fight dominance throughout the game and were far ahead in gold. They went on to push our full HP (yet still weak sauce...) turrets and end the game before we were even up. Towers need a buff and spider needs a nerf IMO... >.<