I think you have selectively narrowed the question to suit your own prejudices here. The loss of confidence of potential lenders (or Bond buyers) for a nation's public debt is a phenomenon the world has observed numerous times in the last century. I don't know of any precise economic model able to reliably predict the occurrence of such a loss of confidence, but note that the event usually surprised all or most of the knowledgable observers at the time it occurred, but was usually treated as a predictable event by self-appointed savants - after the fact.
Such a loss of confidence occurs when potential lenders lose confidence that their loans will be repaid or that their bonds will retain their value. There are several financial indicators involved here, including total debt as a % of GDP; expectations for continued GDP growth or decline; current budget surplus or deficits; and expectations for future government actions to add to or reduce the deficit. There are others as well, but they all involve the quality of the expectations that the bonds will hold their value.
There are as well a host of other factors that, in the short run, influence expectations for the timing of a crisis in the case of countries that, owing to the presence of a dangerous combination of the above indicators, are seen as vulnerable. I don't think there is much sound theory for this aspect of the problem, and am instead focused on the above factors influencing long-term stability or instability and the confidence of lenders.
You have reduced all of this fairly obvious and elementary stuff to the value of the current year operating deficit of a government in need of loans. That you have found poor correlation is no surprise and no victory for any point under discussion here.
Ireland's crisis occurred, despite a relative low level of government debt as a % of GDP, because the government intervened to guarantee the then poorly quantified liabilities of its banks in the wake of the still unfolding collapse of a housing bubble. This led to suddenly high government deficits amidst fast dropping expectations for GDP growth. The country still retains significant economic advantages in terms of a skilled population, and favorable labor market, tax and regulatory conditions for the establishment of new enterprises. If it can get through the next critical few years of austerity while it deals with the effects of the bank guarantee, its prospects for future growth are very good.
Greece is the antithesis in that its crisis was the result of an extended period of high deficits and high debt relative to GDP; a sclerotic over regulated, over subsidized economy with low expectations for sustained growth; and a succession of governments that pandered favors to its constituents paid with public debt often sustained with deceptive financial reporting to both lenders and EU regulators. The population appears still addicted to the illusory "social welfare" spending of former governments and unwilling to face the changes that are clearly required. Its recovery is both distant and uncertain.
My argument was that chronic government deficits; high levels of public debt relative to GDP, combined with excessive labor market regulation and productivity destroying social welfare spending, which can lower GDP growth, are a reliable formula for the creation of conditions leading to the loss of lender confidence and an ensuing financial collapse. The major Eurozsone states provide us with several prominent examples of this combination today. The still unfolding drama of the political reactions to the situation and the competing viewpoints attending it provide a fascinating confirmation as well.
Sadly our present government appears to be determined to mimic the descent of the Eurozone states into a similar morass.
I think you understood all this and my viewpoint perfectly well, and merely indulged in a cheap "gotcha" game with a trivial model of your own creation.