Instruments of War and Hall of Triumph are bad cards, only providing a small anthem effect nothing else for their mana cost isn't good enough to take deck spots
If you are jamming a few Eldrazi Titans and don't want to wait ten turns to cast them, you can power them out on turn six or so with the right ramp package
Getting three or four spiders each time you cast the card isnt hard, and its a must in spider typal decks
Its low mana cost means that any deck along the aggressive to control spectrum can play it, and since its colorless, you can slot it in anywhere and cast it using any color
There was little to no power balancing, with some cards being ridiculously overpowered for their casting cost
I'll admit I was a bit skeptical at first, but in early design we always try things because sometimes, as was the case with DFCs, what seems dubious ends up playing well