Author Gronzig emailed us a note about this new addon of his called RankWatch, which serves a simple purpose: it alerts you if anyone is using downranked spells. I'm sure we've all seen the player who forgets to train, put on their bars, or update their macros with new ranks of important spells. Heck, I was using rank two of Binding Heal well into Naxxramas, since I had it bound directly to a key with Dominos.
If anyone in your party or raid uses a rank lower than the maximum for their level, RankWatch will tell then about it in a whisper. The only exception is for Life Tap, which warlocks will often use rank one of to proc effects without taking much of a health hit. Back in the day, healers would commonly downrank heals as a mana-saving measure (if I recall correctly, Heal rank four was a staple in classic raiding), but this strategy is long-gone (since patch 3.0.2), because downranked spells now cost the same amount mana as top-rank spells (or more).
Configuration options include turing off the auto-whisper and ignoring certain players, which are both vital for a potentially-annoying mod like this. Overall RankWatch looks like a useful little tool, if only so I no longer have to worry about checking up on myself.
Download RankWach at Curse