I wouldn't paint the turians' involvement on Tuchanka as some generous gesture. This was strictly out of self-interest. Victus proposes that they get help from the krogan, who are basically sworn enemies of the empire, and commits some forces to ensure that this plan actually pulls through. His only concern about destabilizing the krogan is that it may drastically affect whether or not he gets the forces he needs. If the Primarch believed that the turians could fight the war without the krogan, he would probably have left them to rot, just like anyone else would.
As for the krogan sending troops to Palaven in the interim, I'm not sure what this would even accomplish except to send a handful of krogan off to die on Palaven as some symbolic gesture. The turians go to Tuchanka to perform some specific tasks to make good on a deal that the Primarch agreed to. There would be no such objective on Palaven.
I never said it was some heartfelt, generous gesture on the Turians part; if I did I would have focused on how Victus lost his son trying to help the Krogan. I'm just pointing out that the Turians provide aid and help accomplish side tasks not even associated with the initial agreement. They are the ones making sure that the Krogans get their cure while the 2 billion Krogan just sit on Tuchanka twiddling their thumbs. What good does holding off aid for Palavan until after the cure is deployed do for anyone, including the Krogan, aside from letting them act all smug now that a "sworn enemy" has to help them now? That's just bad tactics.
For all anyone knew, the Reapers could make a massive push, break the tenuous hold the Turians have over their homeworld, and then fortify it against invasion, thereby rending the Krogan support moot, and dooming the entire galaxy to a slow, agonizing death. Even looking at the best case scenario, how many ships, and personal could have been saved; ships and personnel that could have been used elsewhere in the war; if the Krogan moved forward with deployment as soon as the accord was stuck? The Genophage cure isn't going to matter when the Reapers are bombarding those precious, newborn Krogan from orbit now is it?
It would be like the US refusing to send aid to England or France during WW2 unless they relinquished all extra territoriality to America; like say gold or diamond mines in Africa. And then, when both countries agree to this, the United States waits until they start receiving shipments of gold and diamonds from those holdings before they send a single troop to Europe. That's just asinine, tactically (as well as morally) since if the Axis succeeds then all those mines in Africa won't matter.
How did he "crap" on his nation's allies? When the meeting starts, they are not allies in anything. You want Wrex to send interim troops to Palaven... but keep in mind that it's during that interim he finds out that the Turians planted a bomb on his planet and have left it there for 1,000 years... for what purpose? As others have stated, neither the Turians nor the Krogan are at that table in a "good samaritan" state of mind. It's a tough negotiation driven out of necessity among nations that have a long history of being hostile to each other. In that setting, "good" leaders are going to be "tough" on each other. No one at that table, including the salarians, is being really irrational though given the nature of their relative histories and the nature of the negotiation... and that's why everything can work out in the end.
BTW, what I find really "sad" about that whole meeting is that the human political "leader" couldn't even be bothered to show up... nor even someone with a rank above "commander"... even though the whole premise of the game is "getting help for Earth."... too busy updating his database of notable birthdays, I guess.
Allies? No, but the Turians have been providing Tuchunka with foodstuffs since the Rebellions, and the Salarians have the whole Shroud thing going on. Out of the three of them, two of these species have been aiding the Krogan for the past 1,000 years. The Genophage is irrelevant in this regard; you don't see the Krogan seeking to restore their planet, or grown their own food, those have both been supplied by their "sworn enemies". If the Turians and Salarians really were as antagonistic towards the Krogan, as they are to them, then Tuchunka would have been wiped clean of all life a long time ago.
And the bomb was planted there because the Krogan had just instigated a devastating war with the galaxy, and completely wrecked three Turian garden worlds; the Krogan should know, a good majority of them alive today were around when the Rebellions were going on. Wrex is pushing 900 years, so he should be completely aware of the state of affairs following the conflict. More than that, the government officials who ordered the placement of that device have been dead for the past six or seven generations, at least; the current administration is just cleaning up the mess left by their ancient predecessors.
Though, I agree that the human delegation of just Shepard was disappointing, and even a little insulting. We humans are expecting the Kogan to aid the Turians so that the Turians can aid us; dragging the leaders of both species to the table; and we can only be bothered to send a frontline soldier.