So, a couple things to point out for the OP.
First thing, this is all completely false. Defenders using their attacks are not "weak blasters." In fact, the argument can be made that they're more beneficial than blaster attacks, since Defenders will get more use out of a power's secondary effects. The -ToHit debuffs from Dark Blast, for example, will be significantly more powerful on a Defender than a Blaster because of Defender modifiers. As a Defender, the primary function of your attacks is not to cause damage, but to debuff enemies and make them easier for your team to handle, thus filling the role of support rather well.
With Tankers, there's a similar secondary use to their powers that's not directly stated, and that is the inherent taunt that comes with every Tanker attack. The Tanker's inherent ability of Gauntlet casts a short AoE taunt effect on critters within range with every attack they use. A Tanker running in fists flying will hold aggro significantly better than a Tanker just using Taunt, because every single one of their attacks is also taunting enemies.
Finally, INF earned from defeated enemies is not at all based on damage dealt. This is 100% false, otherwise door-sitting and farming wouldn't exist. If you are on a team, any defeat made by any member of your team will evenly distribute all EXP and INF to every player on the team. Even if that Blaster one-shot a minion all by themselves, everyone on the team gets credit for the defeat. There is no participation threshold for INF or EXP. All EXP, INF, and drops are evenly calculated for every member of the team. Drops are the only instance where there will be variation, but once again, drops are based on random rolls and not on participation. So for example, if a recipe has a 10% chance to drop from an enemy, and the Stalker on the team defeats the enemy in one hit, every member of the team will roll that 10% chance for the recipe, and it may even be awarded to more than one player.
All of this was designed to prevent kill-stealing, last-hitting, participation thresholds, and certain AT's being easier or harder to level on purpose. It's all intentionally designed this way to make the game fun for everyone, and to prevent arguments over loot, exp, inf, and what have you.
As others have stated, City of Heroes is not like any other MMO you've ever played. It's for that reason this game has such a dedicated fanbase, because there really isn't any other game like it on the market. And as stated previously, Tankers hold aggro better when attacking, and in some instances can even be very good DPS in their own right. My Bio/Claws Tanker is a DPS monster, and that's without sacrificing any of his survivability.
With this game, you eventually run into a point where you cannot take any other powers except for your attacks, and by the mid 30s, you'll have so many enhancement slots you won't know where to put them. I always pick and slot my attacks as a Tanker, and it doesn't harm my survivability in any meaningful way. In City of Heroes, a Tanker that is not using their attacks to generate aggro is not tanking as effectively as they could. Run in there and punch things! Make the bad guys mad! You're a TANK, and tanks are just as capable at offense as they are at defense.
And this is one point where I will actually agree with you to an extent. If your gaining INF solely from defeats, then yes, you're going to have a bad time. This is why a lot of players in this thread are giving guides to using the Auction House. One of my only complaints with this game is that INF from defeats is so negligible in the early game that you're pretty much forced to use the market.
But, despite that, the market isn't incredibly difficult or complex to learn, and you don't have to be a super-savvy marketeer to make decent cash off of it. On all of my characters, in the early game, I craft and sell all recipes and IOs that I can't use and sell them on the market. You'd be surprised at just how much INF you can make by just selling your drops at low price on the markets. My Fire/Fire Blaster on redside already has like 30 million INF in her account at level 25, and that's all from just selling drops. I'm not converting or using merits or buying things to flip them, I'm just playing the game and crafting the recipes I find to sell on the market. Even just a single piece of rare salvage sells for around 450K on the market, and I use that money to fund all of my enhancements and slotting.
Once you get higher in level, the INF you get from defeats increases significantly, but in the early game, I will concede that INF generation is pathetic outside of selling drops. Luckily, selling drops is super easy and trivial, and you can make yourself a multi-millionaire in INF from just selling drops on the market. The guides posted here are super helpful, and I would recommend reading them to get a better understanding of how stuff works.