Their increased AC bonus shouldn't be a increase to maximum dexterity to armour limit, it should be a cumulative bonus when using shields, that way a stalwart or DoS would really be able to get more from it's shields. Also AC requirements scale in a way that players usually can't follow, unless they have tons of good equipment for that. Then I thought, why not use AC as a damage reduction factor? Just make it in a way that after some point it gives a bonus damage reduction for each extra point you have, that way AC would matter even for epic content, wich would be scaled up by using the same system. But make it percentages, that way you could have something like this.
AC Reduction
34 0%
35 19%
36 28%
37 34%
38 38%
39 42%
40 44%
41 47%
42 48%
43 50%
44 51%
45 53%
46 54%
47 55%
48 56%
49 57%
50 57%
51 58%
52 59%
53 59%
54 60%
55 61%
56 61%
57 62%
58 62%
59 62%
60 63%
61 63%
62 64%
63 64%
64 64%
65 65%
66 65%
67 65%
68 66%
69 66%
70 66%
71 67%
72 67%
73 67%
74 67%
75 68%
76 68%
77 68%
78 68%
79 68%
80 69%
81 69%
82 69%
83 69%
84 69%
85 70%
86 70%
87 70%
88 70%
89 70%
90 70%
91 71%
92 71%
93 71%
94 71%
95 71%
96 71%
97 71%
98 72%
99 72%
100 72%
or Maybe
34 0%
35 1%
36 2%
37 3%
38 4%
39 5%
40 6%
41 7%
42 8%
43 9%
44 10%
45 11%
46 12%
47 13%
48 14%
49 15%
50 16%
51 17%
52 18%
53 19%
54 20%
55 21%
56 22%
57 23%
58 24%
59 25%
60 26%
61 27%
62 28%
63 29%
64 30%
65 31%
66 32%
67 33%
68 34%
69 35%
70 36%
71 37%
72 38%
73 39%
74 40%
75 41%
76 42%
77 43%
78 44%
79 45%
80 46%
81 47%
82 48%
83 49%
84 50%
85 51%
86 52%
87 53%
88 54%
89 55%
90 56%
91 57%
92 58%
93 59%
94 60%
95 61%
96 62%
97 63%
98 64%
99 65%
100 66%
or
34 0%
35 1%
36 2%
37 3%
38 4%
39 5%
40 6%
41 7%
42 8%
43 9%
44 10%
45 10%
46 11%
47 11%
48 12%
49 12%
50 13%
51 13%
52 14%
53 14%
54 14%
55 15%
56 15%
57 15%
58 16%
59 16%
60 16%
61 17%
62 17%
63 17%
64 17%
65 18%
66 18%
67 18%
68 18%
69 19%
70 19%
71 19%
72 19%
73 19%
74 20%
75 20%
76 20%
77 20%
78 20%
79 21%
80 21%
81 21%
82 21%
83 21%
84 21%
85 22%
86 22%
87 22%
88 22%
89 22%
90 22%
91 23%
92 23%
93 23%
94 23%
95 23%
96 23%
97 23%
98 23%
99 24%
100 24%