Just to add something, apart from the eximus enemies which the spears don't affect, I want to say that 25 meters might have been a lot on early warframe days, but with the new tilests (zariman and cavia), the rooms have become much much bigger, and therefore there's less enemy density. 50 meters is quite a lot, but on the cavia tileset you'll find plenty rooms which you can simply not nuke since they are too big.