I tested in the two places I solo most often: epic chrono and epic into the deep. Those are the places I'm most interested in my solo performance in, since the primary purpose of my caster's soloing is completing claw and abishai sets (or getting scrolls that trade for completing said sets). I chose to stick with the mob I'm most familiar with in order to make it easier to adjust to the changes in both my character and in the monster saving throws themselves. This evades the risk of overreacting becuase you are unfamiliar with the monsters you end up testing against like you've done.
And no, I'm just saying that the dcs you cited are extremely typical numbers for pre-TR-era casters. If you have two sf in Evocation, you should easily be surpassing the 37 dc barrier with what you lay out. My caster is a 36 with 1 pl sorc and 1 pl wizard, but again, Amrath is simply a place of extremely, extremely high saving throws on every monster, especially its explorer zone. You'd be better off testing in a quest (like sins) or in some epic content somewhere (go zap scorps in claw or something). Amrath exp zone mobs have like +30 in every single saving throw, it is absurdly high. Spells do not land on them. Even the best casters don't land on them. You can't test efficacy there.
I'm also bearing in mind that in general casters are gonna be performing worse on Lamannia than on live. For example, I'm down 2 dcs because I forgot to restock Yugoloth pots before transferring (and favor unlocks don't transfer) and because there's no +2 ship buff. 4 charisma is a pretty significant thing, and i can tell you my caster doesn't cast spells very often without one or both of those two things present. The difference between 38-40 cha and 44 cha is significant even on live, and trying to compare yourself on Lamannia to your live variant that's actually running a much higher effective statistic is a great way to overemphasize the saving throw changes made to epic and/or the efficiency of spells. Many casters will be having a very hard time carrying all 3-4 charisma enhancements as they might have previously as well, which might also impact their charisma bracket. One of my testing builds was down another cha bracket from the live version because of those AP problems, and 38 cha and 44 cha sorcerors barely even play the same game.
Also keep in mind there are a wide range of abilities that give monsters effective or direct penalties to saving throws. In addition to the will save debuffs that have be en mentioned in release notes, here are some examples:
Waves of exhaustion on a large mob group is -3 to all their reflex.
Any monster that is dancing from irresistable or otto's dancing sphere recieves -10 reflex save.
Solid fog now has a saveless debuff to reflex saves, the exact magnitude of which I do not know.
Helpless foes also get a penalty to effective reflex save, which means that targets hit by mass hold monster not only take 50% more damage but will fail a lot more saving throws as well. In fact, helpless creatures and players cannot evade or improved evade, so you can hold an evasion monster to make it vulnerable to nuking with your reflex spells. Even if it rolls a 20, it will still take half damage. Even on live I routinely hold archer mobs before pelting them with fireballs to ensure that they will take full damage from every casting.
You can utilize these abilities to force monster reflex saves down to where your reflex-dependent abilities (whether they be slas or simply because you are an air savant) are more, or in many cases nearly completely reliable. After throwing a dancing sphere down, I was able to easily powernuke through significant clumps of mobs with my aoe reflex abilities. If my otto's spheres had actually been cast at my real live enchantment dc of 39 instead of a 36, I suspect that my life would have been significantly improved over what it's presently like on live. With a spell focus: evoc and the passive sorceror past life, I should have a 40-41 evocation dc on live, and will probably not even need the CC other than it's important role in stopping incoming damage while I'm killing 20 fish and scrags at the same time. Any damage bonuses (especially the ones from holds) will just be gravy.