Simply put, yes.
Although, I would recommend the following changes:
Deoxys-A @ Life Orb
EVs: 6 HP / 252 SAtk / 252 Spe
- Psycho Boost
- Signal Beam
- Ice Beam
This set gives Deoxys coverage against the Dark, Flying, Water, Psychic, Fighting, Poison and Dragon types. Due to Deoxys potential to outrun most Pokemon (Only matched in speed by opposing Deoxys-A, N, S and Ninjask) and having such poor defensive stats - making it a hit-and-run Pokemon, the Life Orb is a very suitable item for Deoxys-A.
I personally think that the qualities mentioned above are what make this Deoxys better than the others, but nonetheless your Deoxys-A is quite badass.
Note from Aeternis:
After editing the question to make appear more presentable and easier to read, I myself had a few suggestions to better the content of this answer:
Generally, for all that I'm aware of, Modest / Timid Deoxys' don't tend to be that effective due to Deoxys-A mixed potential being far superior to its one-side sets (all physical / all special). Sets as these are usually bestowed upon its less viable form, Deoxys-N. Though it may seem like an inferior Deoxys-A, the slight boost in its defensive stats do enable it to survive unboosted attacks such as Bullet Punches from Mega Scizors, Mega Lucario and Extreme Speed coming off an Adamant max attack Arceus not wielding an attack enhancing item, while being able to fire back extremely hard and nearly OHKOing- 2HKOing everything in the tier with its extremely powerful attacks. The set I would recommend for this would be the pretty standard Deo-N set of:
Deoxys @ Focus Sash / Mind Plate
EVs: 88 Def / 240 SpA / 180 Spe
- Stealth Rock / Calm Mind
- Psycho Boost
- Shadow Ball
- Hidden Power Fire
You could also still use Deo-A with this set, but then you should either use the Life Orb or the Focus Sash, add the 88 EVs in Defense to its speed and always use Stealth Rock over Calm Mind.