Here's a list of current summoner job issues taken from my post on the summoner forums. I'd like it if the developers could take a look at this list, and fix what they can, or at least let us know what things will/won't be fixed.

Avatars and Spirits:
The Assault command has no effect if your pet is too far away from you

The range of the Assault command (from the summoner to the target) varies by the model scale of the target.
Example:
The assault range on Black Shuck in the Tier 10 Assault "Better than one" is so short that you can get hit by Gates of Hades while at maximum assaulting range.
The assault range on Cerberus in mount zhayolm is so large that at maximum assault range you won't be hit by Gates of Hades.
Black Shuck's model size is much smaller than Cerberus'.

Sometimes when your pet is dead, you will not be able to summon another pet. During this time you get a system message stating that you already have a pet. This issue may be caused by the pet dying from a DoT effect.

Pets can glitch and ignore retreat commands. They will retreat for one second and then resume hitting the target, even if the target is attacking the pet and not the summoner

There are no log messages provided when avatar-generated buffs wear off of of avatars or other party members

Spirit Assumptions:
The spirit comments listed here are all assuming that the old rules of spirit spells still apply:
Spirits don't gain access to self-buff spells (stoneskin, aquaveil, enspells, etc)
Spirits don't gain access to elemental aoe spells
Spirits don't gain access to merited spells
Spirits do gain access to enfeebling/divine/elemental/dark/healing(cure and curaga)/enhancing(regen, protect, shell) magic spells at the minimum level that any other job can learn it.

Spirits:
There are two animations for elemental siphon; the first animation shows MP coming out of a target, the second shows MP going into the target. The first animation currently targets the caster when it should be targeting the elemental.

Using the Assault ability with a spirit sets their timer to max recast.

Spirit spellcasting is easily interrupted. Almost any attack will interrupt them.

Spirit spells are resisted very often. This coincides with the previous issue; they both may be caused by the spirits having a very low magic skill level.

A spirit will re-apply shock, burn etc. even if the monster has it already. This may be because potency of the enfeeble is reduced over time. Either that, or the elemental doesn't check if the monster has the debuff already.

Fire Spirit does not learn Addle

Earth Spirit does not learn Break

Light spirit does not learn Regen 2, 3, 4 or 5

Light spirit does not learn Cure 6

Light spirit does not learn Repose

Light Spirit learns Banish 4 before WHM or PLD.

Dark Spirit does not learn Drain 2 or Aspir 2

Dark spirit does not learn Absorb-ACC, or Absorb-TP

Dark Spirit knows stun even though Stun is of the lightning element

Light spirit can only cast on targets that it's facing. Light spirit does not have a face which makes this difficult

Light spirit behaves differently in Full Moon Fountain. It's able to cast on anyone, no matter which way it's facing, and it's unable to move while casting. (This probably isn't important enough to fix, but thought I'd add it for some cool trivia)


Avatars:
Avatars fail to perform self-targeted blood pacts if their auto-attack target dies

The maximum Blood Pact reduction cap is 15 seconds (25%). This is by far, the strictest cap on increased cooldown/damage potential in the game. The cap for spell recast reduction is 50%. The cap for melee swing time reduction (gear haste/spell haste/JA haste) is 80%. This allows all other jobs to increase their damage output by a much greater margin than summoners can.

Every hit of an avatar's multihit bloodpact will give them full TP for each hit (9-10% TP).

Diabolos loses all his TP with any Blood Pact used (even Ward) when his only TP based BP is Night Terror.

The potency of Diabolos' Noctoshield is the same now as it was at level 75. This means that comparitively it's becoming weaker as we gain more levels. Are there any plans to rectify this by scaling Noctoshield's potency past level 75? (It does scale by level before level 75).

Thunderspark's range from the avatar to the target is larger than the AOE radius of Thunderspark. This also applies to Ultimate Terror.

The Blood Pacts Thunderspark, Lunar Roar, Sleepga, Nightmare, Ultimate Terror, and Slowga have a smaller AOE range than ~ga spells.

Garuda's Aero 2 Blood Pact uses the animation of Aeroga 2

Shiva's Sleepga has the potency of Sleepga 2 (1:30), but has the same tier as Sleep/Sleepga 1. (It can't overwrite Sleep/Sleepga 1)

Carbuncle's Holy Mist animation is the same as Holy 2

Carbuncle and Fenrir are not resistant to their respective elements

No log messages are produced when Lunar Roar removes buffs from enemies.

No log messages are produced when avatar-generated buffs wear off of avatars and party members.

No log messages are produced when avatar-generated enfeebles wear off of enemies.

The extended magic aggro range because of weather is still present in the protocrystals. Meaning, the avatars within the protocrystals will aggro you if you cast magic at twice the normal magic aggro range. This effect of weather was removed from the rest of the zones in the game previously.