Umm triple duration?
+30% from gear and another +50% from composure for 1.50 * 1.30 = 1.95 or 95% duration bonus. 195% duration is less then 300% duration by a fairly large margin. Hyperbole doesn't help your case.
Now to the real problem with using duration bonus, all except the feet and head are replaced by +enh skill items. Body / Legs / Hands are all +15 (hands +18) for a total of 48 skill. Thus for max potency (500 skill) your looking at cape + boots for 30% and another +10% from two emp items. 1.30 * 1.10 = 1.43 or a 43% duration bonus.
For cycling haste your talking three to four (only on melees) haste's per 5:51 seconds, that isn't bad at all and represents a reasonable load from the 75 days. The problem is when you add on ~more~ stuff to the top of those hastes, spells that you won't be using full duration on. Temper is 3min and +1% per 10 skill, Gain-STR is also 3min and +1 per 20 skill. That means 4:17 duration on both Gain-STR and Temper if cast on another party member. Now your casting load is six to eight spells per 4:17 and another three to four per 5:51 seconds. Temper has a long recast, as does Haste. Gain-STR has a relatively short recast but it almost as long as haste for cast time.
Congrats you just turned RDM into a buff monkey doing nearly twice as much cycling as it did at 75.
None of this is an issue when self-cast due to the 3.9x duration bonus making all three of those an 11:42 duration buff along with Enspell.
It would be like a BRD casting marchs individually on each party member.
Now take your foot out of your mouth Oph.