I hear where you're coming from, but...
1) While it's true that casters have more than one save they can target (albeit with limited options depending on the mob type), the vast majority of instakills are fortitude-based. Playing a caster with maxed out spell DCs tends to preclude anything approximating good DPS, so even if we assume (correctly) that a divine can command some things that he can't implode, he's then left with no ability to actually kill the guy he's just commanded.
Targeting weak saves might've made sense when the primary role of a caster was cc and casters had multiple options for that, but it does not make sense in a meta where melees can bring their own cc (with better DCs than casters) and also dps.
2) Yes, the new THF system has had a massive impact on the current meta. It made an already extant problem far worse.
3) Somewhat true, but not an accurate comparison for two reasons
- On a DC caster, DCs are typically your only way to kill something. As such, it's crucial that your DCs are reliable
- Stunning blow is more analogous to soundburst than it is to FoD. A pure DC specced character is using FoD instead of hitting things with a weapon, not instead of using stunning blow.
4) Once again, you're comparing CC to what amounts to a DC casters' ability to kill trash. In the amount of time that it takes FoD to become available, a decent melee could've used some combination of tactics and helpless damage to rip through an entire pack of mobs.
I'm not sure whose theory you're referencing, but I don't think discussing whether or not the tactics/spell DC balance used to make sense is a good way to spend our time. It currently does not, and it would be great if some sort of adjustments could be made.Of course, this was the theory... in practice dire charge exists, and good AOE builds (caster and melee versions) can now nuke R10 mobs in seconds making the above theory moot.