You can get better, sure. IMO, it shouldn't be so much better that an enemy only has a 5% chance of landing an ability against that save. (Not counting very rare one-time enemies like gods, for whom that's fine since it's a one off.)
wait... even with the ring and the paladin you aren't making it on a 2... that is a 5% chance. what are you talking about at best I got it to a 4. (15% chance) and again that is only with your best save...
lets do the standard array.
15, 14, 13, 12, 10, 8
lets put the +1 in the 15 and the +2 in the 14 so I get 2 16s
16 +3
16 +3
13 +1
12 +1
10 +0
8 -1
now lets give prof in 1 of the 16s and the 13. and give a +2 to the 16 with the prof... make them a +4 prof
18 +8
16 +3
13 +5
12 +1
10 +0
8 -1
but then lets give them either a cloak or ring +1
18 +9
16 +4
13 +6
12 +2
10 +1
8 +0
lets forget the scores and just record the saves
+9, +6, +4, +2, +1, +0
lets say that 1/3 of the time you get a +3 from a paly next to you and that brings you to
+12,+9,+7,+5,+4,+3
these two sets gives us a range of +0-+12 where +12 is your best and +0 is your worst... so against a DC 14 you have a 5% fail on your BEST save in the BEST situation, and you have a 65% fail rate on your worst in the worst situation...
prof 4 comes on line between levels 9-12 so lets imagine a threat that should be facing in those levels... do you think having there save based off an 18 or 19 stat is reasonable?
Ideally, the numbers shouldn't normally skew so hard that either side has a 95% chance of success.
but again to skew that hard you have to have a magic+ a prof a good stat and a paladin friend with a good stat... even then most times it wont be 5% fail...
now lets take those numbers and say you will make 40 saves over levels 9-12 (number pulled from my back side but that is 10 saves per level) and that half of them will be against your best save (that seems dubius unless you just happen to have your best save be dex... again I see a rogue issue) but the other 20 saves will be split 10 (so half again) to your next best save and 10 to your third best (you are never useing those last three and again that seems dubius at best but lets see)
so 20saves with +9 66% of the time and +12 33% of the time.
10 saves with +6 66% of the time and +9 33% of the time
10 saves with +4 66% of the time and +7 33% of the time...
now half of those will be DC 13 and half will be DC 15
I will round in favor of the paliden being there...
6 saves +9 Vs 13 (15% chance of fail)
4 saves +12 vs 13 (0% chance of fail)
6 saves +9 vs 15 (25% chance of fail)
4 saves +12 vs 15 (10% chance of fail)
so even here the best save is over those levels .9+1.5+.4=6.4 you come close with 6.4% (lets round down to 6) a 6% fail rate... that rate only goes UP from here... so no it will not be 5% when done but I am tired of doing math for now.
I think that, again ideally, the success rate for both attacker and defender should cap out somewhere around 70% under normal circumstances. That strikes a decent balance between predictability and randomness.
but is that 70% against your best or against your worst? remember even useing this system that is +0-+12 a 12pt swing...
Besides, I've never complained about the 4e treadmill (I think that claim is kind of wrongheaded to begin with)
I agree it only is a treadmill if you ignore all the guidance about encounter building and how attacks themselves scale in damage...
If both attacker and defender are actively improving their respective values, it ought to be a treadmill. Otherwise, you're favoring one over the other (which means devaluing either offense or defense respectively). IMO, if you do want to favor one, it ought to be offense since that makes for a more exciting game.
I would say you should favor the one that is the focus... my BEST save should out distance your DC. my WORST save should be out distanced by your DC, my AVERAGE should be on that treadmill staying about the same...