We speak about migration period from about 376 to 800 AD. It is important because different times make confusion:
http://en.wikipedia.org/wiki/Migration_Period
The
Migration Period, also known as the
Völkerwanderung[1] ("migration of peoples" in
German) or
Barbarian Invasions, was a period of intensified
human migration in
Europe often defined, from the period when it seriously impacted the
Roman world, as running from about 376 to 800 AD
[2][3] during the transition from
Late Antiquity to the
Early Middle Ages. This period was marked by profound changes both within the
Roman Empire and beyond its "
barbarian frontier". The migrants who came first were
Germanic tribes such as the
Goths,
Vandals,
Angles,
Saxons,
Lombards,
Suebi,
Frisii,
Jutes and
Franks; they were later pushed westwards by the
Huns,
Avars,
Slavs,
Bulgars and
Alans.
[4] Later migrations (such as the
Arab conquest and
Viking,
Norman,
Hungarian,
Moorish,
Turkic, and
Mongol invasions) also had significant effects (especially in
North Africa, the
Iberian peninsula,
Anatolia and
Central and
Eastern Europe); however, they are outside the scope of the Migration Period.
...
According different sources Goths can be I1, R1b and R1a carriers. I would not about percentages. Of course they could have other haplogroups. However probability that they were significant I2a-Din-S carriers is minimal.
When the Goths and Slavs arrived to Balkans, Balkan population had I2a haplogroup. Slavs couldn't change it significantly. And R1a existed in Balkans when Slavs arrived. Slavs could significantly change the situation only in the Pannonian Plain.
And I2a is probably older than Ken Nordtvedt suggest. Of course Thracians and Illyrians had this haplogroup, probability would be small in opposite case. Slavs didn't overpopulate mountain ares in Romania, Bulgaria, Serbia, Bosnia, Croatia...
I2a is very significant haplogroup for Balkan, South Slavs and Romanians (division is linguistic-cultural, closeness according to haplogroups is obvious), even in Greece there is significant percentage I2a carriers (North Greece 16%, South Greece 9%!). And this is not due to Slavs (and had nothing to do with the Goths).
And only Geg Albanians (not Tosk Albanians!) in the Balkan are I2a carriers in very small extent, and it distinguish them from the rest of Balkan population. And they probably came the latest in the Balkans, probably from North-East (probably they were non-Balkan population before Christ).
...
What is interesting. I think that
I2a (and generally I) carriers, had own language once, it had to be
pre-IE language! It couldn't be language of R1 carriers. Where we can search this extincit language? In the Balkan? I don't believe in this moment. Maybe we can try others tracks, for example Nuragic language (extinct too, but knowledge exists) in Sardinia.