Olaf is definitely someone I have had a lot of success with. I generally don't go fully tank on Olaf as I typically find him much stronger with 1 damage item on tp of the tank items, but it definitely works. I do not normally have to much of an issue with Olaf not having a gap closer, especially now that you can build righteous glory. So far the only counter I have for for Olaf is garen, but even there its a don't feed and you will out scale type of lane.
Volibear is also pretty good, and works very well full tank, but isn't great if you ever need to carry a team. Still he is a solid pick and I played him a lot before I hit thirty.
Nasus can be very strong if you know how to play him. If the other team doesn't stop you you can get crazy amounts of stacks, build full tank, and do tons of damage. One fun example is a game where I managed to get around 500 stacks by the twenty minute mark, and would half-shot their adc with only spirit visage and frozen heart. He is like Olaf in that he does not have a gap closer, but his wither can be crippling on an adc.
Trundle is great for split pushing, and gets a burst of extra tank stats when you ult someone. Damage falls of late game, but can still be pretty scary.
Shyvana is also a decent pick if you want a tank. She has good initiation and teamfight damage, but lacks crowd control.
Overall I would say try out these uys until you find what you like. I am the same rank as you, but so far this is what works for me when I play top. I would also keep playing wu kong if I were you. As long as you play him when you won't get counter picked, he can do a lot of damage and be a great tank at the same time.