Tips to use Soul Ring Pro and Pubs Games

Soul Ring In Pro Games

Most common place you see Soul Ring is on heroes where it can really expedite your farm. For instance:

Tinker : you get more or less a free re-arm (and Soul Ring is re-armed as well), so you can spam a little more march to farm. Plus, with Boots of Travel you're going to fountain a lot, so the HP loss is negligible.
Enigma : you're farming jungle and taking no damage, so all you need is the mana to keep taking camps. Because you can stay in jungle without going to base, you get levels and gold a lot faster, so you get core items like Mekansm faster.
Dark Seer : spam Ion Shell and control the lane
Beastmaster : core on ancient-ing Beastmaster so you can keep stacking/farming with Wild Axes. It's not as commonplace now because offlane Beastmaster is easy to deal with and mid Beastmaster gets Bottle.
Clinkz : popularized by C9.EE, this gives you a free ult every time its up. That's a lot of extra farm. It also basically guarantees you're never out of mana (whereas your ult can put you low if you just have Orchid Malevolence + Ring of Aquila).

Also, as you mentioned, it was common on Broodmother before she was removed from CM.

You often see it picked up on heroes that:

Are tanky/survivable enough to not care about the HP loss, and need mana
- Ogre Magi : has severe mana issues, can spam and roam easily with it
- Wraith King : has mana issues. Usually you're fine with Power Treads though, just switch to Int and cast. It can work though, but I don't think it's particularly efficient.
Have some sort of built in heal
- Omniknight : severe mana issues, spammable heal
  - On a side note: if you ever offlane Omniknight, Soul Ring is core to zoning the fuck out of any melee carry
- Bane : Brain Sap zoning
- Less commonly: Dazzle (Medallion of Courage is a lot better)
Roamers
- Earthshaker : mana issues, great roamer from level 1, long range init to remove some of the danger of using Soul Ring

Abaddon : I believe Soul Ring is HP Removal, so I cannot remember if that works with Aphotic Shield or his ult Borrowed Time ( HP Removal usually does not count as damage), but Abaddon is a hero that benefits a lot from HP loss (hence why Mask of Madness is popular on semi-carry Abaddon). In any case, he benefits from mana.