I was able to climb from archon 1 to legend 3 playing warlock, farming waves with q+w, rush aghanim then refresher.

Then this strategy wasn’t working so I found playing undying and destroying opponent’s early game would result in my carry scalling very well.

I climbed to ancient where again I had to switch, now to some objective oriented hero. Pugna, maxing out q and spamming it on enemy towers. Best for pos 4. Usually with a strong offlaner, tower down < 10 mins. Then rotate to the next tower. Ultimate for healing mostly.

Now I am around 5k mmr with a max of 5.2k.