ItalianGreyhound - I don't see the relevance of a case in the Republic of Ireland. The law is different there. The other two cases were convictions for GBH with intent, and in one case the accused had previous convictions, so of course the sentencing is much more severe than that in an ABH case. If the defendant in this case had been convicted of GBH or GBH with intent he would have received a much higher sentence - probably 3 years for GBH or 12 years for GBH with intent.
Aeroflotgirl - All the reports concerning the judge's comments originate from a single reporter. There is no way of knowing for sure but I would not be surprised if the judge actually said the victim was not "particularly vulnerable" and the reporter failed to note the word "particularly". On the sentencing guidelines as they currently stand the victim was not "particularly vulnerable", although she was clearly vulnerable. If the report is correct and the judge did just say she was not vulnerable I agree with you.
PandaPolar - There are two main reasons the CPS would accept a plea bargain in a case like this.
Firstly, as you say, it could be that they are concerned that the evidence may not be strong enough to secure a conviction. As he has pleaded guilty he has accepted all the allegations. If he had pleaded not guilty the prosecution would have had to prove them beyond reasonable doubt. If they think they have only got, say, a 55% or 60% chance of getting a conviction a plea bargain may be attractive. A bargain has positives and negatives for both sides. From the prosecution's point of view they have avoided the risk of the defendant being acquitted and have ensured he gets a criminal record, but the record is for a lesser crime than the one he actually committed. From the defendant's point of view he has a lower sentence than he would have received had he been convicted of the more serious offence, but he has given up the chance to defend himself with the possibility of getting a not guilty verdict. Both sides have opted for certainty over the uncertainty of a contested trial.
The other possible reason for accepting a plea bargain is if the victim is seriously unhappy about the prospect of giving evidence in the trial. I don't blame any DV victim who feels that way. In that situation, if the defendant offers to plead guilty to a lesser offence, the victim may be happy for the prosecution to accept the offer so that she does not have to give evidence.