Group H may already be certain that Barcelona will be the group winners if they don't suffer the same fate as last season. However, the other three teams such as Porto, Shakstar, Antwerp are dark horse teams which could become a nightmare for Barcelona at any time. We certainly already know that what is shown in the domestic league is very good but sometimes it is not the same as what is done in the Champions League and Barcelona did that last season. Despite all that, I will still favor Barcelona of course and the runners up will probably be Porto or Shaktar.
Barcelona face easily opponent teams in this group drawing depend last season they have difficult opponent from Bayern Munich until Inter Milan and can't qualified to next round. Its seems difference with this season of group stage opponent teams, Barcelona teams opponent looks not difficult against Porto, Shaktar and Antwerp have bigger chance for the first time in last two season for qualifying to the next round. Opening Champion League matches group stage, Barcelona against Antwerp I think great opportunity for Barcelona first three points in group stage match before facing difficult teams Porto or Shakstar upcoming match.
Looks second standings or runner up position is not difficult for Barcelona in Group H looking with the opponent teams, seems Porto has opportunity will lead 1st or 2nd standings placed in this group.
As you said, Barcelona should not have serious problems when playing their match in the Group H phase. Of the three other teams in Group H, only Porto can make things difficult for Barcelona. however, considering that the Barcelona squad currently has a competitive team. becoming Group H champions, it should be quite easy for them. In fact, Porto is not a scary opponent for a team of Barcelona's level.
If we flashback, last season Barcelona experienced many obstacles that were detrimental to them. apart from the players who were injured after the international break, their opponents were a strong team. even based on H2H, Barcelona always has difficulty when playing matches against Bayern. Unfortunately, Barca was unable to overthrow Inter. which in the end, they slipped. this season, Barcelona will play a match against Royal Antwerp. Three points is a result they must get, both at home and away. Likewise, when Barcelona plays Porto in the next match, they have to win the match. And Barcelona should not waste their momentum to become Group H champions.