I think they did lie to us but only for the sake of keeping secret the playstyle of BLU. Like how you might tell a friend you can't go out because you're working only to surprise them at their party and you were off all along.
Reason being they don't allow DF is that (take me for example) I levelled Blu to 50 and had only water cannon at my disposal. Now what's to stop others doing that and running Aurum Vale or 50 Dngs with just water cannon. They couldn't say that though or else spoil how the spell mechanics would work with finding them etc. SO they claim it is too OP. For some instances it might be (Considering skills don't have levels so you could do sasasha fairly easy with bad Breath and needles etc) bu for the most part it is down to them being unable to control the players themselves and stopping under skilled Blue mages from queuing for duties.

I think if they had a way of making the skills level blocked (for example you cant learn primal skills at 50 until you are level 50)...need an Aurum Vale skill? Well tha Dng is 48 so you need to be 48 to learn it. That enemy is level 18 so you too need to be 18 to learn it. If they could do that you might see a shift to Blue in duties. I don't think the intentionally made it weak bu thought "Lets troll the community and push it as the most OP job ever when really it's trash xD"