I'm checking different cycles using
[Wolfshead Helm] and came up with the following (100 ms latency).
Time Energy Gain
0.1 8 0 Rip
1.2 60 40 Shift
2.3 18 29 Shred
3.2 38 40 Tick
3.3 3 39 Mangle
4.4 60 85 Shift
5.5 18 74 Shred
6.4 38 85 Tick
6.5 3 84 Mangle
7.6 60 130 Shift
8.7 18 119 Shred
9.6 38 130 Tick
9.7 3 129 Mangle
10.8 60 175 Shift
11.9 18 164 Shred
12.8 38 175 Tick
Where gain is the energy difference over time compared against not shifting.
Initial numbers are pretty impressive, but I'm sure it would be pretty hard to maintain 4 shifts per cycle. You would probably need to swap for every type of regen buff -
[Super Mana Potion],
[Superior Mana Oil],
[Elixir of Major Mageblood], Blessing of Wisdom.
[Staff of Natural Fury] could help a lot also, but is an even larger loss in stats than
[Duplicitous Guise]. I haven't done the math, but that might not even be enough for a long fight. Alternating in Mangle makes
[Idol of Terror] and
[Ashtongue Talisman of Equilibrium] valid upgrades though.
I made some 2 and 3 shift variants also. Any less and it's probably not worth using.
2 shift (12.4 sec): 1xMangle, 3xShred
3 shift (13.8 sec): 2xMangle, 4xShred
4 shift (13.2 sec): 3xMangle, 4xShred