Going out sad....
When has Haki been described by anything but strength, or synonyms for strength? Why would Gaban compare it to the Haki at God Valley, if it wasn't for strength? Isn't the strength of conquers Haki what would make Luffy suffocate? No one said anything in relation to the Omen/Maki or whatever it is. Thinking that his slave (Dr Rocks) has weaker Haki than Imu is literal insanity. No, Imu's COC isn't comparable to Roger, Garp, WB etc. He would easily overpower them.
Nope, anything Imu can do counts as his powers. So DR'ing Rocks is a power he canonically has. But either way, he's going to overpower Loki+Luffy, which is better than anything the title merchants have ever done, so....
If it was strength, it would be said so but it never is, because it is merely a hype device, an empty one at that because it is overused at this point.
Fact is, from what we saw so far, Imu never used haki whatsoever, not for a single attack coating, unless, for him specifically, maki achieves the same as haki.
No, when national treasure of MJ is in play, it cannot be counted as Imu's power unless he can wield it in person, when outside of MJ. And I suspect, all the flipping to DR is a power of that treasure and Imu probably cannot use it right now.
The way it looks like is that Imu vs Loki and Imu vs Luffy will be separated fights, one after another so it is not that impressive. Only if he fights them both at the same time for a prolonged period, then it would be better than anything others have done. Right now, his performance is nothing out of ordinary.