This card is almost useless in mono decks.
I've used it in a mono in rushes, dominators, stalls, and stallbreaks -the four major decktypes, in my view of the game. It's useful and normally powerful in any kind of mono-Water.
I prefer to keep my pillars to save quanta for all my Ice Lances.
Ice Lances don't have the sheer damage potential tears do. Ice Lances can't even OTK and they need a whole game's worth of stall to get close. Meanwhile Tears in a rush-heavy deck often kills in 7 turns and in a domin, often 9. It's CC and occasionally PC, but you use it alongside Tears (or other damage) in either a domin or a stall - you would rarely run it alone.
Phoenix can be reborn, and Crimson Dragon doesn't have to sacrifice a Pillar to be summoned.
Crimson Dragon dies to so much. An unupped Nymph can't die to one Lightning, Shockwave, or unupped Rage Potion, and needs 10 quanta to die to Fire Bolt and 20 for the other bolts, plus two uses of Owl's Eye. Upgraded is even more resilent, as you need 10 more quanta for every bolt, an extra use of Owl's Eye, and upgrading to Rage Elixir doesn't help. Soft CC is far more effective against it, and rush and stall monos both have ways to get around that, so neither is typically game over.
As for Phoenixes being reborn, sure, but that CC above tends to slow Phoenix down just as much, if not more. They're both strong resilent damage - Phoenixes build up damage quicker but Nymphs are a better swarmer and therefore stallbreaker.
kinda irrelevant to have icebolts and octopi isnt it? in a mono air rush, people dont pack 6 shockwaves and 3 EEs for a reason
Not completely, their overlap isn't huge, they both do things the other can't.