This isn't always true. RNG can easily screw you pretty hard. Mirror Images can die (it does happen!), the "Passive" talent of L100 feels a lot more active (and is stronger) than the right L100 talent, Rune of Power and Prismatic Crystal... well, I don't even need to explain those
The ONLY tier of talents where you're correct is L75, which is kinda funny how it's the only talent tier of ours (involving DPS) that is well designed (at least for Frost). All 3 talents do well in their own regard and accomplish what is intended.
Also, UM is weak for Frost specifically because of how bad Frostbolt's base damage is (and why FFB is on the list). If it included Multistrikes (bonus chances to proc from MS), Crits (would crit on crits), and Icicle procs on UM, it'd be a lot better.