Nonsense, you are just mad you didn't get your pew pew. It's quite clear to me what it was they were trying to do, which was to avoid making a reskinned warrior.
Balance of the class is a pointless concept. Hybrids were never intended to fulfill primary roles as well as pure classes. If they made a mistake with the paladin is that he should have been a better tank than a healer (while the druid should have been a better healer than a tank, instead it was the other way around). Certainly not a dps class though.
What it was never meant to be was a dress-wearing wimp standing back and spamming FoL and they said as much in the Blizzcon 2005 but that was when the damage was already done, not just from class design perspective but how the image of the Paladins were tainted for years to come in eyes of the community. That is not the Paladin people originally coming from earliel games rolled and that is not the Paladin they had played in Warcraft 2 and 3. There's a reason the iconic Paladin art and gameplay has been that of upgrade from a Knight into most powerful melee character in second game with good anti-undead and healing capabilities and two-handed hammer wielding melee hero attacking/healing hybrid in third.
Addition of Seals play into the downfall of the class because they had perfectly functional and unique system (that they copied almoust 1 to 1 for DK class in WotLK) which was built around simple stack rotation and strong short term buffs. That was all scrapped and what they released was -completely- untested as Seals came around about the same time beta servers went down.
I don't see how getting stuck with healing in raids is a deficiency of the seal system. That was a problem with the idea of what an hybrid class should be as they conceived of it initially, because the ability to fulfill more than one role just not as well as a pure class translated in getting stuck with the one role that didn't need to be maximized, which was healing, and that was true for ALL of the hybrids with healing capabilities, like the druids and the shamans, and unless you want to claim those classes were also finalized at the last minute without "testing", than it's clear the issue was not with the design of the paladin class per-se.
The paladin was also designed after the hero in Warcraft 3, NOT the paladin in Warcraft 2, and the paladin in Warcraft 3 was most definitely a support class. You wanted a dps monster, you went Mountain King.
Alright, first we'll have to establish that there are two distinct versions of Paladin. And I do not speak of the distinction between WC2 and WC3 because that actually matters little.
There is the narrative Paladin and then there's the PvP meta Paladin gameplay for online lobbies or just random matches against AI
The narrative Paladin has always been a frontline fighter with a good support for his allies and this is emphasised through various things. In Warcraft 2 this was elaborated through the gameplay, they were upgrade from the Knight unit and single most powerful melee character of the Alliance, as well as text, describing them just as what they were, valorous knights who had taken into religious crusade against the evil magics of the orcs.
When we come to Warcraft 3, narratively nothing has changed. This too is emphasised through the storyline gameplay that has you constantly fed with items emphasising your melee gameplay as well as your character wielding massive two handed weapon while using Light to shield himself and many story related events having you charge first in line to do your duty through cinematics.
Why this is important? Because we have confirmation that what Blizzard originally intended for the Paladin in WoW was to be the Paladin of the narrative, not the Paladin of the meta gameplay from Warcraft 3 lobbies and expectations when you did play the class and wasn't one of the online players was to be the one to actually stick to melee while supporting your friends from close distance. We have two cases of this;
One is interview with Metzen from before TBC and how he was disappointed in the design direction of the Paladin because the class was never meant to just stand back and heal. They were meant to be at the thick of it, utilizing fast single target heals like Flash of Light and powerful buffs like Blessings for the quick spot heals. That is why all tier items until Naxx emphasised hybrid gameplay in their stats and bonuses.
Another is Blizzcon 2005. When they were talking of the class updates that focused on single class per patch, Blizzard did say that they wanted to bring Paladin into melee. This is the turning point, because at this stage the reputation and the community view of the class had changed. Blizzard were literally booed at because the view of the community had been molded into hating anything that is not a Holy Paladin standing back in dress and healing. This is the turning point because in later interviews after the infamous Paladin 'fix patch' and prior TBC/during TBC launch they outright admitted they wanted to bring Paladin to melee but community response from non-Paladins made them hesitate and just apply some minor changes that altered nothing.
How does this tie back to Seals? We had the narrative Paladin. It was functioning with it's own unique system that relied on short term blessings, they were called the Seals instead before the patch, were more powerful but with shorter duration to have the support gameplay elevated with simple yet effective combat stack system that they copied for Death Knights in WotLK. It was taken away from us and replaced without testing, without oversight on anything how it could affect the class and reception and just to clean the negative it caused meant they spent dev time on fixing shit system that was totally undeveloped instead of focusing on actually fixing fundamental issues of design like they did with most other classes. And when they could've done it the community damage was already done. That is why you kept seeing Paladin revamp over and over again while most other classes got incremental or additive things when game progressed to TBC and through it's patches, and further as well as why most other specs became far more viable faster than say, Prot or Retribution did.
Now we can have discussion about conspiracy about why they did this (Most of the old community was convinced it was because that raid leader from EQ got lead class design role and hated hybrids after they stole his spot as tank in some raid) but I doubt that'd be fruitful at all.
