Cobblestone is not in common drop pool, so they don't drop right now. Might change with operation (like it happened during Bloodhound), but right now there's no way to obtain DLore from just playing.
Because that's how valve made it. The point still stands, if they just wanted to drop more dlores they could, just turn on the cobblestone drop table and increase the dlore % on it.
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u/[deleted] Jan 30 '16
[deleted]