Crystal Maiden's Freezing Field

Well actually Frostbite is pretty much a free Hand of Midas. CM is really one of the rich supports.
1000 damage to any creep. One-shots jungle creeps on a 10 second cooldown.
CM farms pretty fast actually. Blink Dagger/ Black King Bar is prefectly viable, been there done that, and that was before 6.82 where it was only 700 damage. Now it's really oneshotting creeps.

It's really instant farming so it's perfectly compatible with supporting a lane or roaming.

but the thing is,if you are farming, you can't contribute to fights,which is more important than farming for a support in my opinion

Well at the early game, roaming CM usually farm in the jungle with frostbite. It has been done multiple times in competitive, I believe.

*instant* farming.

Leave your safe lane to gank mid, and Frostbite a creep on the way. Or leave your safe lane for 5 seconds, and get a free creep. Ez 100 gold. Rinse and repeat. And get the bounty runes for additional dosh.

It's like having a midas. CM is the new Furion xD

Holla holla get dolla

Of course it is. But Crystal Maiden needs Blink Dagger, Black King Bar, Aghanim's Scepter in order to do this. And the biggest help she can get is from Magnus's Reverse Polarity. In other words:
Reverse Polarity -> Black King Bar -> Blink Dagger -> Freezing Field -> Rampage. Crystal Maiden is not the only one who can do this. Take Sand King for an example.

Sand Storm can deal 8000 DPS at level 1 with 320 enemies inside. The probability of getting 8000 DPS on 8 enemies with Freezing Field is far lower than the probability of getting a 320-target Sand Storm, as it would require all 8 targets being nearly on top of Crystal Maiden and every comet (10 per second) dropping near the minimum range.