heavy armor ac tank, mobility and dodge any good still?

[Feithlin]

As other posters said, the actual situation isn't very clear. You basically need to reach significant values in AC, PRR, dodge, saves, hp and dps. That's a lot to take into account, and with the diminishing results, the max-in-a-single-area may not be the best option.
Another problem is that those values are relative too. For example, the benefit of a toughness feat (after the 1st) depends on your hp total and the benefit you can get from augmenting AC or PRR. 26 hp (toughness + rank III stance) is worth 3.25% if you have 800 hp, but only 2.17% if you have 1,200 hp. Can you get more than this by increasing your PRR or AC (but it only applies to physical damage)?
Maybe the best would be to fix a reference to compare the values, depending on what you're aiming for, and see how much AC/PRR you need to get 1% more mitigation.

About your initial question, dodge is always good as long as you can benefit from it. Since it is limited by your mdb, you will have to know what it can be, which depends on the armor(s) you'll use. For example, on my own tank (Fighter 18/Rogue 2), I think I'll continue to use at least 2 sets: an evasive one, with as much dodge as possible, with significant enough AC/PRR, and a high AC/PRR heavy armor one, in which I must try to slot as much dodge as possible.

Mobility (feat or item) is well worth as it gives 2 more mdb in addition to dodge. Dodge and Spring attack on the other hand are only worth if you can handle their bonuses to dodge. It may free up some gear slots, or on the other hand, you may free up feats by using gear.

The basic idea, with so many variables is to maintain some constant, or put some minimal values, to have an easier overview.

*Edit: Basically, you want this value as high as possible (this your overall physical damage mitigation):

1 - [(1 - %Dodge) * (1 - %AC) * (1 - %PRR)]
P.S. %AC depends on your opponents to-hit

[RadioactivePiranha]

I've seen a couple posts talk about Physical Resistance miss chance. Physical Resistance does not provide any miss chance at all, it reduces physical damage from the hits you do take.