One of the especially cool things about a guitar is the fact that there are almost always at least a few ways to play the same notes.
This fact allows (and forces) us guitarists to explore the different possibilities available through experimentation with alternate fingerings, picking strategies and phrasing. Often, while there are many ways to play the exact same notes, there is usually a “magic” fingering and picking pattern that allows for the easiest and most effective execution of the phrase.
As an advocate of this “following the path of least resistance”-type of efficiency, guitar guru Paul Gilbert has come up with a great deal of influential ideas, but one of his most useful and technically streamlined is that of string skipping arpeggios. With this technique, instead of playing the common “finger-rolled barre” or similarly inefficient sweep picked arpeggio shape depicted in EXAMPLE 1a, you would move the B string note to its equivalent on the G string and switch to alternate picking instead of sweep picking (EXAMPLES 1b and 1c).
EXAMPLES 2a-c and 3a-c show the major and minor flat 5 shapes, respectively.
Note that your roots are both the D string note and the index finger E string note, and that the pattern conveniently has an “outside” picking pattern with all of the down-strokes falling on the downbeats when alternate picking is used.
The efficiency of these shapes can be further enhanced by the use of convenient legato phrasing when adjacent notes are found on the same string. When performing the arpeggios this way, the right hand still moves as if it were alternate picking, simply moving rhythmically without making contact with the string when a note is phrased legato.