Was the heart of Lorkhan more than a power source for the Numidium? Mantella was used as a replacement for the Heart for the Numidium, which points out that hearts mimicking Lorkhan's Heart can be a power source as well. And i guess that the dusty tomes beyond the collapsed passages of some Dwemer ruins may hold knowledge of the procedure, that would make a fine part of a plotline for some TES in-game book.
Fix'd
And yes it was. If it did power Numidium (like Akulakhan, the second Numidium, was going to do as well), then it would've been symbolic of the Dwemer slaving Nirn itself and it's whole function to work for the Dwemer and on their terms to achieve what they wanted to achieve (ascension). As a side effect, that'd mean total dominion over Nirn for the Dwemer. Not that they'd care from their perspective at that point.
And RE: the poll, we know what happened to the Dwemer. Maybe not Rourken Clan, but we know that they disappeared because they were trying to use the Heart of Lorkhan. The better question to ask is "did they succeed or did they fail?"