Yep, a well played wizard who did, in fact, have Planar Binding and Magic Jar!
What did the wizard spend his time doing? If the metric for how powerful a character is is damage dealt, then a wizard who focuses on battlefield control or debuffing is obviously not going to match up, because that's just not his job! There's several ways to contribute to an encounter. One is dealing enough damage to destroy the enemy, but just as valid is possessing an enemy or crippling them to the point where they helplessly eat damage to the face.
I know that psions are better at dealing damage than wizards, but damage dealing with a core (or SRD) wizard isn't great. 1d6/level blasting damage isn't enough to keep up with monster HP, while the inability to swap energy types (unless you're an Archmage) means that there's a decent chance that some of your damage spells will be useless. At level 10, your best damage dealing spells in core are Scorching Ray, Fireball, Lightening Bolt, and Cone of Cold. The AoE deal 10d6 damage each, for an average of 35 damage. 35 damage, reflex save for half, is insufficient. Fortunately, you can empower Fireball so it deals 52.5 damage on average. A maximized Scorching Ray does 48 damage.
An CR 10 11 headed hydra has 118 HP, with fast healing 21. A monstrous scorpion has 150 hp. A Formian Myrmarch has 102 HP, but
Fast healing 2, immunity to cold,
resistance to electricity 10, fire 10, and
sonic 10,
spell resistance 25, all of which cuts down on a blaster's damage output. A noble salamander has 112 hp, immunity to fire, but vulnerability to cold.
It will take about 2-3 rounds to work through most of the monsters on this list with the aforementioned blasting spells.
Of course, you could just Magic Jar the hydra and force it to commit suicide. Charm the scorpion and make it your pet. Use Polymorph to turn the party's rogue into a 10 headed hydra so he can sneak attack ten times per round and brutally kill the Myrmarch. Same for the Noble Salamander; actually, it's worse off as it's armor class is low enough that most of the rogue's attacks hit for 1d10+5+5d6 each, and he has ten of them.
(Fireball and AoE damage spells do get better if you face large groups of enemies since you could clear a room quickly, though.)
Honestly, making blasting better is hardly breaking the game considering it was a little weak in the first place.
This would make a difference to our experience - we were SRD based, so no energy substitution feat, no orb of fire, acid breath or melfs unicorn arrow (don't really know what any of those do!)
Energy Substitution is an SRD feat. It's in the divine section.
Orb of Fire is a spell in the Orb series that includes Acid, Cold, Lightning, Sonic, and Force versions. They are touch attack, 1d6/level (max 15d6) damage ranged attack spells that ignore SR, offer no save vs damage, and have a status effect the target saves against.
Acid Breath is a cone spell that deals 1d6/level (max 10d6) of acid damage, ref save for half. It and the Orb series are the closest analogies I could find to the crystal shard powers that ignore SR.
Melf's Unicorn Arrow creates several projectiles, 1+ 1 every 3 caster levels above 5, to a maximum of 5 arrows. Each one deals 1d8+8 untyped damage, and bull rushes the target. The bullrush effect is stronger the more arrows hit an enemy. At level 17, it's dealing 5d8+50 damage, or 72.5 damage on average. No SR, no save. It's somewhat less suitable for metamagic abuse than the Orb series.
Sure did, it was all within the pp limits. The most problematic character was a metabolic(?) psion, who could buff his hit points to insane levels, take loads of damage and then unleash that untyped damage back on attackers with a touch attack (or something like that - it was several years ago). He also had lots of big damage ignoring SR powers, and things like the power that lets him explode doing masses of damage in a 40ft radius (which is huge on the battlemat)
Sounds pretty powerful. Here's the thing; arcane magic gets the ability to do that too.
Buff hit points? Lots of spells like False Life and Vampiric Touch add temp HP.
Take lots of damage? some spells like Greater Blink drastically increase your survivability.
Big damage, no SR spells? Covered above.
Damage in a 40 ft radius? Wail of the Banshee has that. Horrid Wilting has a 30 ft radius.
Retaliatory attack? It seems like you're talking about
Forced Shared Pain. Not really unbalanced, as it's a Fort: negates. Anyways immediate retaliation is one of the uses for Celerity. Contingency does this as well.
Psionic powers are not generally unbalanced. Sometimes they're different from arcane magic, but that's not the same as broken. While several problems exist, the same could be said for arcane magic (even in core) so the conception that XPH psionics is fundamentally broken is, like my computer, unwarranted.