Ok, everything everyone has said here about tanking stats on weapons and gear is 100%. But I can't help myself questioning your reasoning behind going for the weapons you were mentioning.
I'm going to assume that, as Prot spec, you would like to weapons to dual-wield in order to run instances as non-prot (sounds very wierd to me, but hey, I'll have to run with it, as it's the only reason I can see you want to dual wield as prot)
Bare in mind that any PvP weapon below 2 speed is an off hand weapon ... you can't have 2 of them and dual wield them. On the off chance you did indeed realise this, could you please elaborate on what you mean by "MG 1.6 sec mace" .. I'm having difficulty figuring out what you mean there. If you meant the Merciless Gladiator mace .. again, it's off hand only, and secondly, it's 1.5, not 1.6 (minor detail, I know, but quite relevant ito identifying what weapon you're talking about)
If, however, you're talking about the 2.6 mace (as opposed to the 1.6 mace), then fine, those 2 will do you ok for dual wielding (2x2.6 weapons will be even better though, but it is a lot more expensive), although as mentioned before, you're probably better off speccing fury if that's the style of play you're after ... some people can do decent DPS as prot spec ... but that's because they've got very good dps gear.
There, I'm sure I've covered all possibilties regarding answers to your question, I hope it helps. And yeah - if you want to tank, please don't go into an instance expecting to tank while dual-wielding ... that would be tragic, especially seeing as though your 41 point talent in the prot tree requires a shield.