[RDM Suggestion] AoE Attack Phase

[Rongway]

simply spamming scatter for the same amount of gcd's will net you 300 x 4= 1200 but significantly less mana.

First set of alternating spells: Scatter [3|3] + Veraero [11|0] + Scatter (0.75[3|3] + 0.25[8|8]) + Verthunder [0|11] yields [17|17] - [22|22] mana (expected [18.25|18.25]).
Subsequent sets: Scatter (0.75[3|3] + 0.25[8|8]) + Veraero [11|0] + Scatter (0.75[3|3] + 0.25[8|8]) + Verthunder [0|11] yields [17|17] - [27|27] mana (expected [19.5|19.5]).

First set of 4xScatter is [3|3] + 3(0.75[3|3] + 0.25[8|8]), or [12|12] - [27|27] (expected [15.75|15.75])
Subsequent sets are 4(0.75[3|3] + 0.25[8|8]), [12|12] - [32|32] (expected [17|17]).

Here's a more readable table

                            Min        Max        Expected
Alternating (1st set)       [17|17]    [22|22]    [18.25|18.25]
Alternating (after 1st)     [17|17]    [27|27]    [19.5 |19.5 ]
Scatter spam (1st set)      [12|12]    [27|27]    [15.75|15.75]
Scatter spam (after 1st)    [12|12]    [32|32]    [17   |17   ]

Alternating spells guarantees [5|5] more than the minimum, but expected values are only [2.5|2.5] apart. Alternating spells are expected to generate more mana, but will only grant one extra E.Moulinet per twelve spells compared to full Scatter spam.

Alternating on a group of 3 (and, in some cases, larger groups) is a good idea, but the best reason is to keep a stronger mob even with the rest of the group; not necessarily because of the extra mana generation.