Why wouldn't they have been I2a2 ? This haplogroup was present in the Illyrian region at least since the Mesolithic.
well, how can Illyrian language go completelly out of use in a group that is genetically extremelly homogeneous and lives in isolated mountain areas as people from Herzegovina do... that is just very difficult to explain.. in all languages where population went through large cultural and language shifts there are layers and layers of previous language, but I donnot think that is the case for Herzegovina...in fact, when Serb language reformer Vuk Stefanovic Karadzic (
http://en.wikipedia.org/wiki/Vuk_Stefanovi%C4%87_Karad%C5%BEi%C4%87) was creating 100% phonetic alphabet, and grammar rules for Serbian literature language, he used language spoken in Herzegovina as basis, as he concluded that it is the area where most pure Serbian language is spoken...
to compare, there are still Vlach villages scattered over Balkan, who kept their language (that originates from times of Roman empire) despite them being scattered around... now if they kept complete language, how come that people in Herzegovina, who are grouped in single place and genetically very homogeneous, did not keep anything from their language?
I find that hard to believe....
So, in my opinion, either I2a2 came mostly with Slavs, or previous people did already speak similar or in fact the same language...
btw. Albania is full with Slavic toponyms...one could argue that Slavs have massively settled in that land as well, but as far as I remember there is an issue that when trying to connect Albanian language related toponyms to the ones of ancient world, it goes only via Slavic intermediary form...
on other hand, some toponyms in south Serbia and Macedonia seems to have Albanian root....
so, I find it possible that Albanians origin from Dardanians, and south Slavic people from Illyrians....
in fact, one may conclude that also based on this:
http://4.bp.blogspot.com/_Ish7688voT0/TNLyVNbffHI/AAAAAAAAC0E/vsEQYTTobHQ/s1600/Ystrclusters.png
http://dienekes.blogspot.com/2010/11/clustering-of-european-y-strs.html
which shows that south Slavs cluster with Romanians, east and west Hungary and central Ukraine...
if we look at cluster and try to figure out possible source of this spread, south part of central Ukraine seems logical... and exactly there we find Vinnitsya area which in fact likely means area of Veneti...
http://en.wikipedia.org/wiki/Vinnytsia_Oblast
Veneti are by many scholars thought to be same as Illyrians...
and when Jordanes writes of early Slavs he tells that they are of Veneti race...
Hermanaric also took arms against the Venethi. This people, though despised in war, was strong in numbers and tried to resist him. But a multitude of cowards is of no avail, particularly when God permits an armed multitude to attack them. These people, as we started to say at the beginning of our account or catalogue of nations, though off-shoots from one stock, have now three names, that is, Venethi, Antes and Sclaveni.
In the land of Scythia to the westward dwells, first of all, the race of the Gepidae, surrounded by great and famous rivers. For the Tisia flows through it on the north and northwest, and on the southwest is the great Danube. On the east it is cut by the Flutausis, a swiftly eddying stream that sweeps whirling into the Ister's waters. (34) Within these rivers lies Dacia, encircled by the lofty Alps as by a crown. Near their left ridge, which inclines toward the north, and beginning at the source of the Vistula, the populous race of the Venethi dwell, occupying a great expanse of land. Though their names are now dispersed amid various clans and places, yet they are chiefly called Sclaveni and Antes. (35) The abode of the Sclaveni extends from the city of Noviodunum and the lake called Mursianus to the Danaster, and northward as far as the Vistula. They have swamps and forests for their cities. The Antes, who are the bravest of these peoples dwelling in the curve of the sea of Pontus, spread from the Danaster to the Danaper, rivers that are many days' journey apart. (36) But on the shore of Ocean, where the floods of the river Vistula empty from three mouths, the Vidivarii dwell, a people gathered out of various tribes. Beyond them the Aesti, a subject race, likewise hold the shore of Ocean.
http://people.ucalgary.ca/~vandersp/Courses/texts/jordgeti.html